Due to its great potential applications in thermal management,heat control,and quantum information,phononics has gained increasing attentions since the first publication in Rev.Mod.Phys.841045(2012).Many theoretical a...Due to its great potential applications in thermal management,heat control,and quantum information,phononics has gained increasing attentions since the first publication in Rev.Mod.Phys.841045(2012).Many theoretical and experimental progresses have been achieved in the past decade.In this paper,we first give a critical review of the progress in thermal diodes and transistors,especially in classical regime.Then,we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics.In the third part,we discuss the potential applications.Last but not least,we point out the outlook and challenges ahead.展开更多
Thermal transistor,the thermal analog of an electronic transistor,is one of the most important thermal devices for microscopic-scale heat manipulating.It is a three-terminal device,and the heat current flowing through...Thermal transistor,the thermal analog of an electronic transistor,is one of the most important thermal devices for microscopic-scale heat manipulating.It is a three-terminal device,and the heat current flowing through two terminals can be largely controlled by the temperature of the third one.Dynamic response plays an important role in the application of electric devices and also thermal devices,which represents the devices’ability to treat fast varying inputs.In this paper,we systematically study two typical dynamic responses of a thermal transistor,i.e.,the response to a step-function input(a switching process)and the response to a square-wave input.The role of the length L of the control segment is carefully studied.It is revealed that when L is increased,the performance of the thermal transistor worsens badly.Both the relaxation time for the former process and the cutoff frequency for the latter one follow the power-law dependence on L quite well,which agrees with our analytical expectation.However,the detailed power exponents deviate from the expected values noticeably.This implies the violation of the conventional assumptions that we adopt.展开更多
Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean...Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean free paths of acoustic phonons, the engineering of phonon spectra at the nanoscale becomes an important topic. Phonon manipulation allows for active control and management of heat fow, enabling functions such as regulated heat transport. At the same time, phonon transmission, as a novel signal transmission method, holds great potential to revolutionize modern industry like microelectronics technology, and boasts wide-ranging applications. Unlike fermions such as electrons, polarity regulation is difficult to act on phonons as bosons, making the development of effective phonon modulation methods a daunting task.This work reviews the development of phonon engineering and strategies of phonon manipulation at different scales, reports the latest research progress of nanophononic devices such as thermal rectifiers, thermal transistors, thermal memories, and thermoelectric devices,and analyzes the phonon transport mechanisms involved. Lastly, we survey feasible perspectives and research directions of phonon engineering. Thermoelectric analogies, external field regulation, and acousto-optic co-optimization are expected to become future research hotspots.展开更多
The combination of different nanostructures can hinder phonons transmission in a wide frequency range and further reduce the thermal conductivity(TC).This will benefit the improvement and application of thermoelectric...The combination of different nanostructures can hinder phonons transmission in a wide frequency range and further reduce the thermal conductivity(TC).This will benefit the improvement and application of thermoelectric conversion,insulating materials and thermal barrier coatings,etc.In this work,the effects of nanopillars and Ge nanoparticles(GNPs)on the thermal transport of Si nanowire(SN)are investigated by nonequilibrium molecular dynamics(NEMD)simulation.By analyzing phonons transport behaviors,it is confirmed that the introduction of nanopillars leads to the occurrence of lowfrequency phonons resonance,and nanoparticles enhance high-frequency phonons interface scattering and localization.The results show that phonons transport in the whole frequency range can be strongly hindered by the simultaneous introduction of nanopillars and nanoparticles.In addition,the effects of system length,temperature,sizes and numbers of nanoparticles on the TC are investigated.Our work provides useful insights into the effective regulation of the TC of nanomaterials.展开更多
We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic str...We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic structures,Fermi-surface quantum fluctuations,as well as phonon properties of the antiferromagnetic kagome metal FeGe.It is found that charge density wave emerges in such a system due to a subtle cooperation between electron-electron interactions and electron–phonon couplings,which gives rise to an unusual scenario of interaction-triggered phonon instabilities,and eventually yields a charge density wave(CDW)state.We further show that,in the CDW phase,the ground-state current density distribution exhibits an intriguing star-of-David pattern,leading to flux density modulation.The orbital fluxes(or current loops)in this system emerge as a result of the subtle interplay between magnetism,lattice geometries,charge order,and spin-orbit coupling(SOC),which can be described by a simple,yet universal,tight-binding theory including a Kane-Mele-type SOC term and a magnetic exchange interaction.We further study the origin of the peculiar step-edge states in FeGe,which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.展开更多
Through equilibrium and non-equilibrium molecular dynamics simulations,we have demonstrated the inhibitory effect of composition graded interface on thermal transport behavior in lateral heterostructures.Specifically,...Through equilibrium and non-equilibrium molecular dynamics simulations,we have demonstrated the inhibitory effect of composition graded interface on thermal transport behavior in lateral heterostructures.Specifically,we investigated the influence of composition gradient length and heterogeneous particles at the silicene/germanene(SIL/GER)heterostructure interface on heat conduction.Our results indicate that composition graded interface at the interface diminishes the thermal conductivity of the heterostructure,with a further reduction observed as the length increases,while the effect of the heterogeneous particles can be considered negligible.To unveil the influence of composition graded interface on thermal transport,we conducted phonon analysis and identified the presence of phonon localization within the interface composition graded region.Through these analyses,we have determined that the decrease in thermal conductivity is correlated with phonon localization within the heterostructure,where a stronger degree of phonon localization signifies poorer thermal conductivity in the material.Our research findings not only contribute to understanding the impact of interface gradient-induced phonon localization on thermal transport but also offer insights into the modulation of thermal conductivity in heterostructures.展开更多
Grasping the underlying mechanisms behind the low lattice thermal conductivity of materials is essential for the efficient design and development of high-performance thermoelectric materials and thermal barrier coatin...Grasping the underlying mechanisms behind the low lattice thermal conductivity of materials is essential for the efficient design and development of high-performance thermoelectric materials and thermal barrier coating materials.In this paper,we present a first-principles calculations of the phonon transport properties of Janus Pb_(2)PAs and Pb_(2)SbAs monolayers.Both materials possess low lattice thermal conductivity,at least two orders of magnitude lower than graphene and h-BN.The room temperature thermal conductivity of Pb_(2)SbAs(0.91 W/m K)is only a quarter of that of Pb_(2)PAs(3.88 W/m K).We analyze in depth the bonding,lattice dynamics,and phonon mode level information of these materials.Ultimately,it is determined that the synergistic effect of low group velocity due to weak bonding and strong phonon anharmonicity is the fundamental cause of the intrinsic low thermal conductivity in these Janus structures.Relative regular residual analysis further indicates that the four-phonon processes are limited in Pb_(2)PAs and Pb_(2)SbAs,and the three-phonon scattering is sufficient to describe their anharmonicity.In this study,the thermal transport properties of Janus Pb_(2)PAs and Pb_(2)SbAs monolayers are illuminated based on fundamental physical mechanisms,and the low lattice thermal conductivity endows them with the potential applications in the field of thermal barriers and thermoelectrics.展开更多
The drive for efficient thermal management has intensified with the miniaturization of electronic devices.This study explores the modulation of phonon transport within graphene by introducing silicon nanoparticles inf...The drive for efficient thermal management has intensified with the miniaturization of electronic devices.This study explores the modulation of phonon transport within graphene by introducing silicon nanoparticles influenced by van der Waals forces.Our approach involves the application of non-equilibrium molecular dynamics to assess thermal conductivity while varying the interaction strength,leading to a noteworthy reduction in thermal conductivity.Furthermore,we observe a distinct attenuation in length-dependent behavior within the graphene-nanoparticles system.Our exploration combines wave packet simulations with phonon transmission calculations,aligning with a comprehensive analysis of the phonon transport regime to unveil the underlying physical mechanisms at play.Lastly,we conduct transient molecular dynamics simulations to investigate interfacial thermal conductance between the nanoparticles and the graphene,revealing an enhanced thermal boundary conductance.This research not only contributes to our understanding of phonon transport but also opens a new degree of freedom for utilizing van der Waals nanoparticle-induced resonance,offering promising avenues for the modulation of thermal properties in advanced materials and enhancing their performance in various technological applications.展开更多
Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional path...Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation.展开更多
We conduct a theoretical analysis of the massive and tunable Goos–Hänchen(GH) shift on a polar crystal covered with periodical black phosphorus(BP)-patches in the THz range. The surface plasmon phonon polaritons...We conduct a theoretical analysis of the massive and tunable Goos–Hänchen(GH) shift on a polar crystal covered with periodical black phosphorus(BP)-patches in the THz range. The surface plasmon phonon polaritons(SPPPs), which are coupled by the surface phonon polaritons(SPh Ps) and surface plasmon polaritons(SPPs), can greatly increase GH shifts.Based on the in-plane anisotropy of BP, two typical metasurface models are designed and investigated. An enormous GH shift of about-7565.58 λ_(0) is achieved by adjusting the physical parameters of the BP-patches. In the designed metasurface structure, the maximum sensitivity accompanying large GH shifts can reach about 6.43 × 10^(8) λ_(0)/RIU, which is extremely sensitive to the size, carrier density, and layer number of BP. Compared with a traditional surface plasmon resonance sensor, the sensitivity is increased by at least two orders of magnitude. We believe that investigating metasurface-based SPPPs sensors could lead to high-sensitivity biochemical detection applications.展开更多
In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the ...In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the mechanism is still under debate.Here,we report a detailed investigation of the superconducting properties near the QCP(x≈0.7) by utilizing scanning tunneling microscopy and spectroscopy.The temperature-dependent superconducting gap and magnetic vortex state were obtained and analyzed in the framework of the Bardeen-Cooper-Schrieffer model.The ideal isotropic s-wave superconducting gap excludes the long-speculated nematic fluctuations while preferring strong electron-phonon coupling as the mechanism for T_(C) enhancement near the QCP.The lower than expected gap ratio of Δ/(k_(B) T_(C)) is rooted in the fact that Ba_(1-x)Sr_(x)Ni_(2)As_(2) falls into the dirty limit with a serious pair breaking effect similar to the parent compound.展开更多
Nanoscale light sources with high speed of electrical modulation and low energy consumption are key components for nanophotonics and optoelectronics.The record-high carrier mobility and ultrafast carrier dynamics of g...Nanoscale light sources with high speed of electrical modulation and low energy consumption are key components for nanophotonics and optoelectronics.The record-high carrier mobility and ultrafast carrier dynamics of graphene make it promising as an atomically thin light emitter which can be further integrated into arbitrary platforms by van der Waals forces.However,due to the zero bandgap,graphene is difficult to emit light through the interband recombination of carriers like conventional semiconductors.Here,we demonstrate ultrafast thermal light emitters based on suspended graphene/hexagonal boron nitride(Gr/hBN)heterostructures.Electrons in biased graphene are significantly heated up to 2800 K at modest electric fields,emitting bright photons from the near-infrared to the visible spectral range.By eliminating the heat dissipation channel of the substrate,the radiation efficiency of the suspended Gr/hBN device is about two orders of magnitude greater than that of graphene devices supported on SiO2or hBN.Wefurther demonstrate that hot electrons and low-energy acoustic phonons in graphene are weakly coupled to each other and are not in full thermal equilibrium.Direct cooling ofhigh-temperature hot electrons to low-temperature acoustic phonons is enabled by the significant near-field heat transfer at the highly localized Gr/hBN interface,resulting in ultrafast thermal emission with up to 1 GHz bandwidth under electrical excitation.It is found thatsuspending the Gr/hBN heterostructures on the SiO2trenches significantly modifies the light emission due to the formation of the optical cavity and showed a~440%enhancement inintensity at the peak wavelength of 940 nm compared to the black-body thermal radiation.The demonstration of electrically driven ultrafast light emission from suspended Gr/hBNheterostructures sheds the light on applications of graphene heterostructures in photonicintegrated circuits,such as broadband light sources and ultrafast thermo-optic phase modulators.展开更多
A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an H_(2)O-D_(2)O mixture.Results have been obtained and analyzed in the concentration range of 0%-10%and 90%-10...A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an H_(2)O-D_(2)O mixture.Results have been obtained and analyzed in the concentration range of 0%-10%and 90%-100%D_(2)O.A proposed structure of tungsten scatterers in an aluminum host is studied.In order to detect the target material,a cavity region is considered as a sound wave resonator in which the target material with different concentrations of D_(2)O is embedded.By changing the concentration of D_(2)O in the H_(2)O-D_(2)O mixture,the resonance frequency undergoes a frequency shift.Each 1%change in D_(2)O concentration in the H_(2)O-D_(2)O mixture causes a frequency change of about 120 Hz.The finite element method is used as the numerical method to calculate and analyze the natural frequencies and transmission spectra of the proposed sensor.The performance evaluation index shows a high Q factor up to 1475758 and a high sensitivity up to 13075,which are acceptable values for sensing purposes.The other figures of merit related to the detection performance also indicate high-quality performance of the designed sensor.展开更多
In the study of Terrestrial Gamma-ray Flashes (TGFs) and Sonoluminescence, we observe parallels with larger cosmic events. Specifically, sonoluminescence involves the rapid collapse of bubbles, which closely resembles...In the study of Terrestrial Gamma-ray Flashes (TGFs) and Sonoluminescence, we observe parallels with larger cosmic events. Specifically, sonoluminescence involves the rapid collapse of bubbles, which closely resembles gravitational collapse in space. This observation suggests the potential formation of low-density quantum black holes. These entities, which might be related to dark matter, are thought to experience a kind of transient evaporation similar to Hawking radiation seen in cosmic black holes. Consequently, sonoluminescence could be a valuable tool for investigating phenomena typically linked to cosmic scale events. Furthermore, the role of the Higgs boson is considered in this context, possibly connecting it to both TGFs and sonoluminescence. This research could enhance our understanding of the quantum mechanics of black holes and their relation to dark matter on Earth.展开更多
The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective...The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective of thermoelectric applications. The calculations were performed after analytical expressions, obtained in the frame of a physical model, more detailed than the model presented earlier by authors. The main Hamiltonian of the model includes the electronic and phonon part, electron-phonon interactions and the impurity scattering term. In order to estimate the electric charge transport between the molecular chains, the physical model was upgraded to the so-called three-dimen- sional (3D) physical model. Numeric computations were performed to determine the electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric power factor and thermoelectric figure-of-merit as a function on charge carrier concentrations, temperatures and impurity concentrations. A detailed analysis of charge-lattice interaction, consisting of the exploration of the Peierls structural transition in TCNQ molecular chains of TTT(TCNQ)<sub>2</sub> was performed. As result, the critical transition temperature was determined. The dispersion of renormalized phonons was examined in detail.展开更多
This article provides an overview of underwater sound-absorbing materials mainly applied with polyurethane matrix.It mainly elaborates on the underwater sound mecha-nism,commonly used underwater sound-absorbing materi...This article provides an overview of underwater sound-absorbing materials mainly applied with polyurethane matrix.It mainly elaborates on the underwater sound mecha-nism,commonly used underwater sound-absorbing materials and structures,as well as new underwater sound-absorbing material structures derived from local resonance pho-nonic crystals,such as phononic crystals,local resonance phonon wood piles,and meta-material sound-absorbing structures.This provides a broader development space and direction for the future development of underwater sound-absorbing materials.展开更多
Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest.Here we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-pla...Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest.Here we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-plane ferroelectric material,enables a dynamical amplification of the electric polarization within subpicoseconds time domain.Our first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode,pumped to nonlinear regimes,spontaneously generates in-plane motions,leading to rectified oscillations in the in-plane electric polarization.We suggest that this dynamical control of ferroelectric material,by nonlinear phonon excitation,can be utilized to achieve ultrafast control of the photovoltaic or other nonlinear optical responses.展开更多
We systematically investigate the phonon dichroism in proximitized graphene with broken time-reversal symmetry.We find that in the absence of any type of spin–orbit coupling,phonon dichroism vanishes.Linear and circu...We systematically investigate the phonon dichroism in proximitized graphene with broken time-reversal symmetry.We find that in the absence of any type of spin–orbit coupling,phonon dichroism vanishes.Linear and circular phonon dichroism occur in the presence of uniform(staggered)intrinsic spin–orbit coupling and ferromagnetic(antiferromagnetic)exchange coupling.All these situations can be distinguished by their specific behaviors of phonon absorption at the transition point.Our finding provides new possibilities to use phonon dichroism to identify the form of spin–orbit coupling and exchange coupling in proximitized graphene on various magnetic substrates.展开更多
The investigations of surface waves in the piezoelectric medium bring out great possibility in designing smart surface acoustic wave(SAW)devices.It is important to study the dispersion properties and manipulation mech...The investigations of surface waves in the piezoelectric medium bring out great possibility in designing smart surface acoustic wave(SAW)devices.It is important to study the dispersion properties and manipulation mechanism of surface waves in the semi-infinite piezoelectric medium connected with periodic arrangement of shunting circuits.In this study,the extended Stroh formalism is developed to theoretically analyze the dispersion relations of surface waves under different external circuits.The band structures of both the Rayleigh wave and the Bleustein-Gulyaev(BG)wave can be determined and manipulated with proper electrical boundary conditions.Furthermore,the electromechanical coupling effects on the band structures of surface waves are discussed to figure out the manipulation mechanism of adjusting electric circuit.The results indicate that the proposed method can explain the propagation behaviors of surface waves under the periodic electrical boundary conditions,and can provide an important theoretical guidance for designing novel SAW devices and exploring extensive applications in practice.展开更多
Diamond is a wide-bandgap semiconductor with a variety of crystal configurations,and has the potential applications in the field of high-frequency,radiation-hardened,and high-power devices.There are several important ...Diamond is a wide-bandgap semiconductor with a variety of crystal configurations,and has the potential applications in the field of high-frequency,radiation-hardened,and high-power devices.There are several important polytypes of diamonds,such as cubic diamond,lonsdaleite,and nanotwinned diamond(NTD).The thermal conductivities of semiconductors in high-power devices at different temperatures should be calculated.However,there has been no reports about thermal conductivities of cubic diamond and its polytypes both efficiently and accurately based on molecular dynamics(MD).Here,using interatomic potential of neural networks can provide obvious advantages.For example,comparing with the use of density functional theory(DFT),the calculation time is reduced,while maintaining high accuracy in predicting the thermal conductivities of the above-mentioned three diamond polytypes.Based on the neuroevolution potential(NEP),the thermal conductivities of cubic diamond,lonsdaleite,and NTD at 300 K are respectively 2507.3 W·m^(-1)·K^(-1),1557.2 W·m^(-1)·K^(-1),and 985.6 W·m^(-1)·K^(-1),which are higher than the calculation results based on Tersoff-1989 potential(1508 W·m^(-1)·K^(-1),1178 W·m^(-1)·K^(-1),and 794 W·m^(-1)·K^(-1),respectively).The thermal conductivities of cubic diamond and lonsdaleite,obtained by using the NEP,are closer to the experimental data or DFT data than those from Tersoff-potential.The molecular dynamics simulations are performed by using NEP to calculate the phonon dispersions,in order to explain the possible reasons for discrepancies among the cubic diamond,lonsdaleite,and NTD.In this work,we propose a scheme to predict the thermal conductivity of cubic diamond,lonsdaleite,and NTD precisely and efficiently,and explain the differences in thermal conductivity among cubic diamond,lonsdaleite,and NTD.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.62004211)Shenzhen Science and Technology Program(Grant No.RCBS20200714114858221)
文摘Due to its great potential applications in thermal management,heat control,and quantum information,phononics has gained increasing attentions since the first publication in Rev.Mod.Phys.841045(2012).Many theoretical and experimental progresses have been achieved in the past decade.In this paper,we first give a critical review of the progress in thermal diodes and transistors,especially in classical regime.Then,we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics.In the third part,we discuss the potential applications.Last but not least,we point out the outlook and challenges ahead.
基金Project supported by the National Natural Science Foundation of China(Grant No.12075316)the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(Grant No.21XNH091)(Q.R.)。
文摘Thermal transistor,the thermal analog of an electronic transistor,is one of the most important thermal devices for microscopic-scale heat manipulating.It is a three-terminal device,and the heat current flowing through two terminals can be largely controlled by the temperature of the third one.Dynamic response plays an important role in the application of electric devices and also thermal devices,which represents the devices’ability to treat fast varying inputs.In this paper,we systematically study two typical dynamic responses of a thermal transistor,i.e.,the response to a step-function input(a switching process)and the response to a square-wave input.The role of the length L of the control segment is carefully studied.It is revealed that when L is increased,the performance of the thermal transistor worsens badly.Both the relaxation time for the former process and the cutoff frequency for the latter one follow the power-law dependence on L quite well,which agrees with our analytical expectation.However,the detailed power exponents deviate from the expected values noticeably.This implies the violation of the conventional assumptions that we adopt.
基金supported by the National Natural Science Foundation of China Grant Nos. 52276072 and 51976096。
文摘Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean free paths of acoustic phonons, the engineering of phonon spectra at the nanoscale becomes an important topic. Phonon manipulation allows for active control and management of heat fow, enabling functions such as regulated heat transport. At the same time, phonon transmission, as a novel signal transmission method, holds great potential to revolutionize modern industry like microelectronics technology, and boasts wide-ranging applications. Unlike fermions such as electrons, polarity regulation is difficult to act on phonons as bosons, making the development of effective phonon modulation methods a daunting task.This work reviews the development of phonon engineering and strategies of phonon manipulation at different scales, reports the latest research progress of nanophononic devices such as thermal rectifiers, thermal transistors, thermal memories, and thermoelectric devices,and analyzes the phonon transport mechanisms involved. Lastly, we survey feasible perspectives and research directions of phonon engineering. Thermoelectric analogies, external field regulation, and acousto-optic co-optimization are expected to become future research hotspots.
基金Project supported by the National Natural Science Foundation of China (Grant No.52076080)the Natural Science Foundation of Hebei Province of China (Grant No.E2020502011)。
文摘The combination of different nanostructures can hinder phonons transmission in a wide frequency range and further reduce the thermal conductivity(TC).This will benefit the improvement and application of thermoelectric conversion,insulating materials and thermal barrier coatings,etc.In this work,the effects of nanopillars and Ge nanoparticles(GNPs)on the thermal transport of Si nanowire(SN)are investigated by nonequilibrium molecular dynamics(NEMD)simulation.By analyzing phonons transport behaviors,it is confirmed that the introduction of nanopillars leads to the occurrence of lowfrequency phonons resonance,and nanoparticles enhance high-frequency phonons interface scattering and localization.The results show that phonons transport in the whole frequency range can be strongly hindered by the simultaneous introduction of nanopillars and nanoparticles.In addition,the effects of system length,temperature,sizes and numbers of nanoparticles on the TC are investigated.Our work provides useful insights into the effective regulation of the TC of nanomaterials.
基金supported by the National Natural Science Foundation of China(Grant No.12174257)the National Key R&D program of China(Grant No.2020YFA0309601)+1 种基金the Science and Technology Commission of the Shanghai Municipality(Grant No.21JC1405100)the Start-Up Grant of ShanghaiTech University。
文摘We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic structures,Fermi-surface quantum fluctuations,as well as phonon properties of the antiferromagnetic kagome metal FeGe.It is found that charge density wave emerges in such a system due to a subtle cooperation between electron-electron interactions and electron–phonon couplings,which gives rise to an unusual scenario of interaction-triggered phonon instabilities,and eventually yields a charge density wave(CDW)state.We further show that,in the CDW phase,the ground-state current density distribution exhibits an intriguing star-of-David pattern,leading to flux density modulation.The orbital fluxes(or current loops)in this system emerge as a result of the subtle interplay between magnetism,lattice geometries,charge order,and spin-orbit coupling(SOC),which can be described by a simple,yet universal,tight-binding theory including a Kane-Mele-type SOC term and a magnetic exchange interaction.We further study the origin of the peculiar step-edge states in FeGe,which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.
基金Project supported by the National Natural Science Foundation of China (Grant No.12104291)。
文摘Through equilibrium and non-equilibrium molecular dynamics simulations,we have demonstrated the inhibitory effect of composition graded interface on thermal transport behavior in lateral heterostructures.Specifically,we investigated the influence of composition gradient length and heterogeneous particles at the silicene/germanene(SIL/GER)heterostructure interface on heat conduction.Our results indicate that composition graded interface at the interface diminishes the thermal conductivity of the heterostructure,with a further reduction observed as the length increases,while the effect of the heterogeneous particles can be considered negligible.To unveil the influence of composition graded interface on thermal transport,we conducted phonon analysis and identified the presence of phonon localization within the interface composition graded region.Through these analyses,we have determined that the decrease in thermal conductivity is correlated with phonon localization within the heterostructure,where a stronger degree of phonon localization signifies poorer thermal conductivity in the material.Our research findings not only contribute to understanding the impact of interface gradient-induced phonon localization on thermal transport but also offer insights into the modulation of thermal conductivity in heterostructures.
基金Project supported by the Youth Science and Technology Talent Project of Hunan Province of China (Grant No.2022RC1197)the National Natural Science Foundation of China (Grant No.52372260)。
文摘Grasping the underlying mechanisms behind the low lattice thermal conductivity of materials is essential for the efficient design and development of high-performance thermoelectric materials and thermal barrier coating materials.In this paper,we present a first-principles calculations of the phonon transport properties of Janus Pb_(2)PAs and Pb_(2)SbAs monolayers.Both materials possess low lattice thermal conductivity,at least two orders of magnitude lower than graphene and h-BN.The room temperature thermal conductivity of Pb_(2)SbAs(0.91 W/m K)is only a quarter of that of Pb_(2)PAs(3.88 W/m K).We analyze in depth the bonding,lattice dynamics,and phonon mode level information of these materials.Ultimately,it is determined that the synergistic effect of low group velocity due to weak bonding and strong phonon anharmonicity is the fundamental cause of the intrinsic low thermal conductivity in these Janus structures.Relative regular residual analysis further indicates that the four-phonon processes are limited in Pb_(2)PAs and Pb_(2)SbAs,and the three-phonon scattering is sufficient to describe their anharmonicity.In this study,the thermal transport properties of Janus Pb_(2)PAs and Pb_(2)SbAs monolayers are illuminated based on fundamental physical mechanisms,and the low lattice thermal conductivity endows them with the potential applications in the field of thermal barriers and thermoelectrics.
基金funded in parts by the National Natural Science Foundation of China (Grant No.12105242)Yunnan Fundamental Research Project (Grant Nos.202201AT070161 and 202301AW070006)support from the Graduate Scientific Research and Innovation Fund of Yunnan University (Grant No.KC-22221060)。
文摘The drive for efficient thermal management has intensified with the miniaturization of electronic devices.This study explores the modulation of phonon transport within graphene by introducing silicon nanoparticles influenced by van der Waals forces.Our approach involves the application of non-equilibrium molecular dynamics to assess thermal conductivity while varying the interaction strength,leading to a noteworthy reduction in thermal conductivity.Furthermore,we observe a distinct attenuation in length-dependent behavior within the graphene-nanoparticles system.Our exploration combines wave packet simulations with phonon transmission calculations,aligning with a comprehensive analysis of the phonon transport regime to unveil the underlying physical mechanisms at play.Lastly,we conduct transient molecular dynamics simulations to investigate interfacial thermal conductance between the nanoparticles and the graphene,revealing an enhanced thermal boundary conductance.This research not only contributes to our understanding of phonon transport but also opens a new degree of freedom for utilizing van der Waals nanoparticle-induced resonance,offering promising avenues for the modulation of thermal properties in advanced materials and enhancing their performance in various technological applications.
基金Project supported by the National Natural Science Foundation of China (Grant No.52106099)the Natural Science Foundation of Shandong Province (Grant No.ZR2022YQ57)the Taishan Scholars Program。
文摘Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation.
基金Project supported by the Natural Science Foundation of Heilongjiang Province of China (Grant No.LH2020A014)the Graduate Students' Research Innovation Project of Harbin Normal University (Grant No.HSDSSCX2022-47)。
文摘We conduct a theoretical analysis of the massive and tunable Goos–Hänchen(GH) shift on a polar crystal covered with periodical black phosphorus(BP)-patches in the THz range. The surface plasmon phonon polaritons(SPPPs), which are coupled by the surface phonon polaritons(SPh Ps) and surface plasmon polaritons(SPPs), can greatly increase GH shifts.Based on the in-plane anisotropy of BP, two typical metasurface models are designed and investigated. An enormous GH shift of about-7565.58 λ_(0) is achieved by adjusting the physical parameters of the BP-patches. In the designed metasurface structure, the maximum sensitivity accompanying large GH shifts can reach about 6.43 × 10^(8) λ_(0)/RIU, which is extremely sensitive to the size, carrier density, and layer number of BP. Compared with a traditional surface plasmon resonance sensor, the sensitivity is increased by at least two orders of magnitude. We believe that investigating metasurface-based SPPPs sensors could lead to high-sensitivity biochemical detection applications.
基金Project supported by the National Key R&D Program of China (Grant Nos. 2022YFA1403203, 2022YFA1403400, and 2021YFA1400400)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302802)+2 种基金the National Natural Science Foundation of China (Grant Nos. 12074002, 12104004, 12204008, and 12374133)the Chinese Academy of Sciences (Grant Nos. XDB33000000 and GJTD-2020-01)the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No. ZR2021ZD01)。
文摘In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the mechanism is still under debate.Here,we report a detailed investigation of the superconducting properties near the QCP(x≈0.7) by utilizing scanning tunneling microscopy and spectroscopy.The temperature-dependent superconducting gap and magnetic vortex state were obtained and analyzed in the framework of the Bardeen-Cooper-Schrieffer model.The ideal isotropic s-wave superconducting gap excludes the long-speculated nematic fluctuations while preferring strong electron-phonon coupling as the mechanism for T_(C) enhancement near the QCP.The lower than expected gap ratio of Δ/(k_(B) T_(C)) is rooted in the fact that Ba_(1-x)Sr_(x)Ni_(2)As_(2) falls into the dirty limit with a serious pair breaking effect similar to the parent compound.
基金supported by the National Natural Science Foundation of China(Nos.12174444 and 52202195)the Natural Science Foundation of Hunan Province(2020RC3032)。
文摘Nanoscale light sources with high speed of electrical modulation and low energy consumption are key components for nanophotonics and optoelectronics.The record-high carrier mobility and ultrafast carrier dynamics of graphene make it promising as an atomically thin light emitter which can be further integrated into arbitrary platforms by van der Waals forces.However,due to the zero bandgap,graphene is difficult to emit light through the interband recombination of carriers like conventional semiconductors.Here,we demonstrate ultrafast thermal light emitters based on suspended graphene/hexagonal boron nitride(Gr/hBN)heterostructures.Electrons in biased graphene are significantly heated up to 2800 K at modest electric fields,emitting bright photons from the near-infrared to the visible spectral range.By eliminating the heat dissipation channel of the substrate,the radiation efficiency of the suspended Gr/hBN device is about two orders of magnitude greater than that of graphene devices supported on SiO2or hBN.Wefurther demonstrate that hot electrons and low-energy acoustic phonons in graphene are weakly coupled to each other and are not in full thermal equilibrium.Direct cooling ofhigh-temperature hot electrons to low-temperature acoustic phonons is enabled by the significant near-field heat transfer at the highly localized Gr/hBN interface,resulting in ultrafast thermal emission with up to 1 GHz bandwidth under electrical excitation.It is found thatsuspending the Gr/hBN heterostructures on the SiO2trenches significantly modifies the light emission due to the formation of the optical cavity and showed a~440%enhancement inintensity at the peak wavelength of 940 nm compared to the black-body thermal radiation.The demonstration of electrically driven ultrafast light emission from suspended Gr/hBNheterostructures sheds the light on applications of graphene heterostructures in photonicintegrated circuits,such as broadband light sources and ultrafast thermo-optic phase modulators.
文摘A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an H_(2)O-D_(2)O mixture.Results have been obtained and analyzed in the concentration range of 0%-10%and 90%-100%D_(2)O.A proposed structure of tungsten scatterers in an aluminum host is studied.In order to detect the target material,a cavity region is considered as a sound wave resonator in which the target material with different concentrations of D_(2)O is embedded.By changing the concentration of D_(2)O in the H_(2)O-D_(2)O mixture,the resonance frequency undergoes a frequency shift.Each 1%change in D_(2)O concentration in the H_(2)O-D_(2)O mixture causes a frequency change of about 120 Hz.The finite element method is used as the numerical method to calculate and analyze the natural frequencies and transmission spectra of the proposed sensor.The performance evaluation index shows a high Q factor up to 1475758 and a high sensitivity up to 13075,which are acceptable values for sensing purposes.The other figures of merit related to the detection performance also indicate high-quality performance of the designed sensor.
文摘In the study of Terrestrial Gamma-ray Flashes (TGFs) and Sonoluminescence, we observe parallels with larger cosmic events. Specifically, sonoluminescence involves the rapid collapse of bubbles, which closely resembles gravitational collapse in space. This observation suggests the potential formation of low-density quantum black holes. These entities, which might be related to dark matter, are thought to experience a kind of transient evaporation similar to Hawking radiation seen in cosmic black holes. Consequently, sonoluminescence could be a valuable tool for investigating phenomena typically linked to cosmic scale events. Furthermore, the role of the Higgs boson is considered in this context, possibly connecting it to both TGFs and sonoluminescence. This research could enhance our understanding of the quantum mechanics of black holes and their relation to dark matter on Earth.
文摘The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective of thermoelectric applications. The calculations were performed after analytical expressions, obtained in the frame of a physical model, more detailed than the model presented earlier by authors. The main Hamiltonian of the model includes the electronic and phonon part, electron-phonon interactions and the impurity scattering term. In order to estimate the electric charge transport between the molecular chains, the physical model was upgraded to the so-called three-dimen- sional (3D) physical model. Numeric computations were performed to determine the electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric power factor and thermoelectric figure-of-merit as a function on charge carrier concentrations, temperatures and impurity concentrations. A detailed analysis of charge-lattice interaction, consisting of the exploration of the Peierls structural transition in TCNQ molecular chains of TTT(TCNQ)<sub>2</sub> was performed. As result, the critical transition temperature was determined. The dispersion of renormalized phonons was examined in detail.
文摘This article provides an overview of underwater sound-absorbing materials mainly applied with polyurethane matrix.It mainly elaborates on the underwater sound mecha-nism,commonly used underwater sound-absorbing materials and structures,as well as new underwater sound-absorbing material structures derived from local resonance pho-nonic crystals,such as phononic crystals,local resonance phonon wood piles,and meta-material sound-absorbing structures.This provides a broader development space and direction for the future development of underwater sound-absorbing materials.
基金We further acknowledge financial support from the European Research Council(ERC-2015-AdG-694097)the Clusters of Excellence Advanced Imaging of Matter(AIM,EXC 2056,ID 390715994)+2 种基金Grupos Consolidados(IT1249-19),and SFB925.D.S.acknowledges the support from National Research Foundation of Korea(NRF-2019R1A6A3A03031296)N.P.was supported by National Research Foundation of Korea(NRF-2019R1A2C2089332)The Flatiron Institute is a division of the Simons Foundation.
文摘Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest.Here we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-plane ferroelectric material,enables a dynamical amplification of the electric polarization within subpicoseconds time domain.Our first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode,pumped to nonlinear regimes,spontaneously generates in-plane motions,leading to rectified oscillations in the in-plane electric polarization.We suggest that this dynamical control of ferroelectric material,by nonlinear phonon excitation,can be utilized to achieve ultrafast control of the photovoltaic or other nonlinear optical responses.
基金supported by the National Natural Science Foundation of China(Grant No.11904062)the Starting Research Fund from Guangzhou University(Grant No.RQ2020076)Guangzhou Basic Research Program,jointed funded by Guangzhou University(Grant No.202201020186)。
文摘We systematically investigate the phonon dichroism in proximitized graphene with broken time-reversal symmetry.We find that in the absence of any type of spin–orbit coupling,phonon dichroism vanishes.Linear and circular phonon dichroism occur in the presence of uniform(staggered)intrinsic spin–orbit coupling and ferromagnetic(antiferromagnetic)exchange coupling.All these situations can be distinguished by their specific behaviors of phonon absorption at the transition point.Our finding provides new possibilities to use phonon dichroism to identify the form of spin–orbit coupling and exchange coupling in proximitized graphene on various magnetic substrates.
基金supported by the National Natural Science Foundation of China(Nos.11890681 and 12232001)。
文摘The investigations of surface waves in the piezoelectric medium bring out great possibility in designing smart surface acoustic wave(SAW)devices.It is important to study the dispersion properties and manipulation mechanism of surface waves in the semi-infinite piezoelectric medium connected with periodic arrangement of shunting circuits.In this study,the extended Stroh formalism is developed to theoretically analyze the dispersion relations of surface waves under different external circuits.The band structures of both the Rayleigh wave and the Bleustein-Gulyaev(BG)wave can be determined and manipulated with proper electrical boundary conditions.Furthermore,the electromechanical coupling effects on the band structures of surface waves are discussed to figure out the manipulation mechanism of adjusting electric circuit.The results indicate that the proposed method can explain the propagation behaviors of surface waves under the periodic electrical boundary conditions,and can provide an important theoretical guidance for designing novel SAW devices and exploring extensive applications in practice.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.62004141 and 52202045)the Fundamental Research Funds for the Central Universities,China (Grant Nos.2042022kf1028 and 2042023kf0112)+2 种基金the Knowledge Innovation Program of Wuhan-Shuguang,China (Grant Nos.2023010201020243 and 2023010201020255)the Natural Science Foundation of Hubei Province,China (Grant No.2022CFB606)the Guangdong Basic and Applied Basic Research Fund:Guangdong–Shenzhen Joint Fund,China (Grant No.2020B1515120005)。
文摘Diamond is a wide-bandgap semiconductor with a variety of crystal configurations,and has the potential applications in the field of high-frequency,radiation-hardened,and high-power devices.There are several important polytypes of diamonds,such as cubic diamond,lonsdaleite,and nanotwinned diamond(NTD).The thermal conductivities of semiconductors in high-power devices at different temperatures should be calculated.However,there has been no reports about thermal conductivities of cubic diamond and its polytypes both efficiently and accurately based on molecular dynamics(MD).Here,using interatomic potential of neural networks can provide obvious advantages.For example,comparing with the use of density functional theory(DFT),the calculation time is reduced,while maintaining high accuracy in predicting the thermal conductivities of the above-mentioned three diamond polytypes.Based on the neuroevolution potential(NEP),the thermal conductivities of cubic diamond,lonsdaleite,and NTD at 300 K are respectively 2507.3 W·m^(-1)·K^(-1),1557.2 W·m^(-1)·K^(-1),and 985.6 W·m^(-1)·K^(-1),which are higher than the calculation results based on Tersoff-1989 potential(1508 W·m^(-1)·K^(-1),1178 W·m^(-1)·K^(-1),and 794 W·m^(-1)·K^(-1),respectively).The thermal conductivities of cubic diamond and lonsdaleite,obtained by using the NEP,are closer to the experimental data or DFT data than those from Tersoff-potential.The molecular dynamics simulations are performed by using NEP to calculate the phonon dispersions,in order to explain the possible reasons for discrepancies among the cubic diamond,lonsdaleite,and NTD.In this work,we propose a scheme to predict the thermal conductivity of cubic diamond,lonsdaleite,and NTD precisely and efficiently,and explain the differences in thermal conductivity among cubic diamond,lonsdaleite,and NTD.