We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contribution...We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contributions from various optical-phonon modes to the ground state energy as functions of the well width and Mg composition. In our calculations, we considered the effects of confined optical phonon modes, interface-optical phonon modes, and half-space phonon modes, as well as the anisotropy of the electron effective band mass, phonon frequency, and dielectric constant. Our numerical results indicate that the electron–optical phonon interactions importantly affect the polaronic energies in the ZnO/MgxZn1-xO quantum well. The electron–optical phonon interactions decrease the polaron energies. For quantum wells with narrower wells, the interface optical phonon and half-space phonon modes contribute more to the polaronic energies than the confined phonon modes. However, for wider quantum wells, the total contribution to the polaronic energy mainly comes from the confined modes. The contributions of the various phonon modes to the transition energy change differently with increasing well width. The contribution of the half-space phonons decreases slowly as the QW width increases, whereas the contributions of the confined and interface phonons reach a maximum at d ≈ 5.0 nm and then decrease slowly. However,the total contribution of phonon modes to the transition energy is negative and increases gradually with the QW width of d.As the composition x increases, the total contribution of phonons to the ground state energies increases slowly, but the total contributions of phonons to the transition energies decrease gradually. We analyze the physical reasons for these behaviors in detail.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
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
The properties of a bound polaron in a parabolic quantum dot with weak electron-LO-phonon coupling under a Coulomb field are studied. The ground state energy of the bound polaron is derived by using a linear combinati...The properties of a bound polaron in a parabolic quantum dot with weak electron-LO-phonon coupling under a Coulomb field are studied. The ground state energy of the bound polaron is derived by using a linear combination operator and the perturbation method. The influence of the interaction between phonons with different wave vectors in the recoil process on the ground state energy of the bound polaron is discussed. Numerical calculations are performed,and the results show that the ground state energy increases significantly as the effective confinement length of the quantum dot decreases,considering of the interaction between phonons. When l0〉1.0, the influence of the interaction between phonons on the ground state energy cannot be ignored.展开更多
The kink structure in the quasiparticle spectrum of electrons in graphene observed at 200 me V below the Fermi level by angle-resolved photoemission spectroscopy(ARPES) was claimed to be caused by a tight-binding el...The kink structure in the quasiparticle spectrum of electrons in graphene observed at 200 me V below the Fermi level by angle-resolved photoemission spectroscopy(ARPES) was claimed to be caused by a tight-binding electron–phonon(e–ph) coupling in the previous theoretical studies. However, we numerically find that the e–ph coupling effect in this approach is too weak to account for the ARPES data. The former agreement between this approach and the ARPES data is due to an enlargement of the coupling constant by almost four times.展开更多
We investigate the effects of pre-stress and surface tension on the electron–acoustic phonon scattering rate and the mobility of rectangular silicon nanowires. With the elastic theory and the interaction Hamiltonian ...We investigate the effects of pre-stress and surface tension on the electron–acoustic phonon scattering rate and the mobility of rectangular silicon nanowires. With the elastic theory and the interaction Hamiltonian for the deformation potential, which considers both the surface energy and the acoustoelastic effects, the phonon dispersion relation for a stressed nanowire under spatial confinement is derived. The subsequent analysis indicates that both surface tension and pre-stress can dramatically change the electron–acoustic phonon interaction. Under a negative(positive) surface tension and a tensile(compressive) pre-stress, the electron mobility is reduced(enhanced) due to the decrease(increase) of the phonon energy as well as the deformation-potential scattering rate. This study suggests an alternative approach based on the strain engineering to tune the speed and the drive current of low-dimensional electronic devices.展开更多
The search for new two-dimensional(2 D)harvesting materials that directly convert(waste)heat into electricity has received increasing attention.In this work,thermoelectric(TE)properties of monolayer square-Au_(2)S are...The search for new two-dimensional(2 D)harvesting materials that directly convert(waste)heat into electricity has received increasing attention.In this work,thermoelectric(TE)properties of monolayer square-Au_(2)S are accurately predicted using a parameter-free ab initio Boltzmann transport formalism with fully considering the spin–orbit coupling(SOC),electron–phonon interactions(EPIs),and phonon–phonon scattering.It is found that the square-Au_(2)S monolayer is a promising room-temperature TE material with an n-type(p-type)figure of merit ZT=2.2(1.5)and an unexpected high n-type ZT=3.8 can be obtained at 600 K.The excellent TE performance of monolayer square-Au_(2)S can be attributed to the ultralow lattice thermal conductivity originating from the strong anharmonic phonon scattering and high power factor due to the highly dispersive band edges around the Fermi level.Additionally,our analyses demonstrate that the explicit treatments of EPIs and SOC are highly important in predicting the TE properties of monolayer square-Au_(2)S.The present findings will stimulate further the experimental fabrication of monolayer square-Au_(2)S-based TE materials and offer an in-depth insight into the effect of SOC and EPIs on TE transport properties.展开更多
The unexplored terahertz (THz) region involves important phenomena of both fundamental and applied natures. Examples include phonon interactions, rotational transitions and intermolecular dynamics. Frequency tunable h...The unexplored terahertz (THz) region involves important phenomena of both fundamental and applied natures. Examples include phonon interactions, rotational transitions and intermolecular dynamics. Frequency tunable high power THz wave generation has been successfully achieved utilizing lattice resonance of LiNbO3 and GaP crystals, respectively. Semiconductor devices utilizing electron tunneling effect have also been developed.展开更多
We describe a scheme for universal quantum computation with Majorana fermions. We investigate two possible dissipative couplings of Majorana fermions to external systems, including metallic leads and local phonons. Wh...We describe a scheme for universal quantum computation with Majorana fermions. We investigate two possible dissipative couplings of Majorana fermions to external systems, including metallic leads and local phonons. While the dissipation when coupling to metallic leads to uninteresting states for the Majorana fermions, we show that coupling the Majorana fermions to local phonons allows to generate arbitrary dissipations and therefore universal quantum operations on a single QuBit that can be enhanced by additional two-QuBit operations.展开更多
The nonequilibrium Kondo effect is studied in a molecule quantum dot coupled asymmetrically to two ferromagnetic electrodes by employing the nonequilibrium Green function technique. The current-induced deformation of ...The nonequilibrium Kondo effect is studied in a molecule quantum dot coupled asymmetrically to two ferromagnetic electrodes by employing the nonequilibrium Green function technique. The current-induced deformation of the molecule is taken into account, modeled as interactions with a phonon system, and phonon-assisted Kondo satellites arise on both sides of the usual main Kondo peak. In the antiparallel electrode configuration, the Kondo satellites can be split only for the asymmetric dot-lead couplings, distinguished from the parallel configuration where splitting also exists, even though it is for symmetric case. We also analyze how to compensate the splitting and restore the suppressed zero-bias Kondo resonance. It is shown that one can change the TMR ratio significantly from a negative dip to a positive peak only by slightly modulating a local external magnetic field, whose value is greatly dependent on the electron-phonon coupling strength.展开更多
We show that a current-carrying coherent electron conductor can be treated as an effective bosonic energy reservoir involving different types of electron–hole pair excitations.For weak electron–boson coupling,hybrid...We show that a current-carrying coherent electron conductor can be treated as an effective bosonic energy reservoir involving different types of electron–hole pair excitations.For weak electron–boson coupling,hybrid energy transport between nonequilibrium electrons and bosons can be described by a Landauer-like formula.This allows for unified account of a variety of heat transport problems in hybrid electron–boson systems.As applications,we study the non-reciprocal heat transport between electrons and bosons,thermoelectric current from a cold-spot,and electronic cooling of the bosons.Our unified framework provides an intuitive way of understanding hybrid energy transport between electrons and bosons in their weak coupling limit.It opens the way of nonequilibrium reservoir engineering for efficient energy control between different quasi-particles at the nanoscale.展开更多
The temperature and LO phonon effects of the bipolaron in polar semiconductor quantum dots (QDs) are studied by using the Tokuda modified linear-combination operator method and the Lee-Low-Pines variational method. ...The temperature and LO phonon effects of the bipolaron in polar semiconductor quantum dots (QDs) are studied by using the Tokuda modified linear-combination operator method and the Lee-Low-Pines variational method. The expressions for the mean number ofLO phonons and the effective mass of the bipolaron are derived. Numerical results show that the mean number of LO phonons of the bipolaron decreases with increasing the temperature and the relative distance r between two electrons, but increases with increasing the electron-phonon coupling strength a The effective mass of the bipolaron M* increases rapidly with increasing the relative distance r between two electrons when r is smaller, and it reaches a maximum at r ≈ 4.05rp, while after that, 34* decreases slowly with increasing r. The effective mass of the bipolaron M' decreases with increasing the temperature. The electron-phonon coupling strength a markedly influences the changes of mean number of LO phonons and the effective mass M* with the relative distance r and the temperature parameter y.展开更多
A theory of ultrasonic generation via direct interaction of transverse optic (TO) phonons with photons in anharmonic lattice of ionic crystals is presented. There are two methods of supplying light energy for the exci...A theory of ultrasonic generation via direct interaction of transverse optic (TO) phonons with photons in anharmonic lattice of ionic crystals is presented. There are two methods of supplying light energy for the excitation of TO lattice wave as a high frequency ultrasound: (A) incident light comes from the source outside the cavity? fulfilled with ionic crystal medium, (B) photon mode of the cavity possesses the gain of amplification by stimulated radiation of active atoms doping in the medium. More attention is drawn to the case (B). The working system of case (B), as a mixture of lasing action and ultrasonic generation, has the threshold phenomena like usual laser. And the linear stability analysis shows that the nonlineax phonon-photon coupling and the interaction among phonons themselves, both of which reflect the anharmonicity of lattice vibration, are necessary to the stable ultrasonic output. So this laser-ultrasonic generation mixture would be also a measure to investigate the lattice-dynamic nonlinearity and correlated electromagnetic properties of ionic crystals.展开更多
We investigate terahertz radiation (T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang Rhys factor of pentacene is also carried out. The results...We investigate terahertz radiation (T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exeiton transferring to the vibrational excited state via electron-phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simDle device at room temperature.展开更多
Recently, emerging phonon phenomena have been discovered and rapidly developed, which have become an active hot research topic. In this review article, we present state-of-the-art advances in several fascinating phono...Recently, emerging phonon phenomena have been discovered and rapidly developed, which have become an active hot research topic. In this review article, we present state-of-the-art advances in several fascinating phonon transport phenomena. First, we summarize the recent progress on the wave nature of phonons, including phonon coherence and its effects on thermal conductivity and the topological properties of phonons. Then, we discuss the particle nature of phonons, including the weak coupling of phonons and the high-order phonon anharmonicity. Finally, we present the summary and a brief outlook. This review presents the advanced understanding of some emerging phonon phenomena in solid materials, which provides new opportunities for further advancement in a wide variety of applications.展开更多
The investigation of the polar optical vibration modes in semiconductor superlattices by different models are reviewed. It is emphasized that the simple analytic representations of the lattice modes calculated with th...The investigation of the polar optical vibration modes in semiconductor superlattices by different models are reviewed. It is emphasized that the simple analytic representations of the lattice modes calculated with the dipole oscillator model have introduced the double boundary condition that both the electrostatic potential and optical displacement vanish at the interfaces and have found wide acceptance. They have been referred to as the Huang Zhu model. It is pointed out that its improved simulation version is essentially the dielectric continuum model taking account of phonon dispersion and subject to the double boundary condition.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11264027 and 11364030)the Project of Prairie Excellent Specialist of Inner Mongolia,Chinathe "Thousand,Hundred and Ten" Talent Training Project Foundation of Inner Mongolia Normal University,China(Grant No.RCPY-2-2012-K-039)
文摘We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contributions from various optical-phonon modes to the ground state energy as functions of the well width and Mg composition. In our calculations, we considered the effects of confined optical phonon modes, interface-optical phonon modes, and half-space phonon modes, as well as the anisotropy of the electron effective band mass, phonon frequency, and dielectric constant. Our numerical results indicate that the electron–optical phonon interactions importantly affect the polaronic energies in the ZnO/MgxZn1-xO quantum well. The electron–optical phonon interactions decrease the polaron energies. For quantum wells with narrower wells, the interface optical phonon and half-space phonon modes contribute more to the polaronic energies than the confined phonon modes. However, for wider quantum wells, the total contribution to the polaronic energy mainly comes from the confined modes. The contributions of the various phonon modes to the transition energy change differently with increasing well width. The contribution of the half-space phonons decreases slowly as the QW width increases, whereas the contributions of the confined and interface phonons reach a maximum at d ≈ 5.0 nm and then decrease slowly. However,the total contribution of phonon modes to the transition energy is negative and increases gradually with the QW width of d.As the composition x increases, the total contribution of phonons to the ground state energies increases slowly, but the total contributions of phonons to the transition energies decrease gradually. We analyze the physical reasons for these behaviors in detail.
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.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The properties of a bound polaron in a parabolic quantum dot with weak electron-LO-phonon coupling under a Coulomb field are studied. The ground state energy of the bound polaron is derived by using a linear combination operator and the perturbation method. The influence of the interaction between phonons with different wave vectors in the recoil process on the ground state energy of the bound polaron is discussed. Numerical calculations are performed,and the results show that the ground state energy increases significantly as the effective confinement length of the quantum dot decreases,considering of the interaction between phonons. When l0〉1.0, the influence of the interaction between phonons on the ground state energy cannot be ignored.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10574063,11275097,10935001,11274166,and 11075075)the National Basic Research Program of China(Grant No.2012CB921504)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.2012009111002)
文摘The kink structure in the quasiparticle spectrum of electrons in graphene observed at 200 me V below the Fermi level by angle-resolved photoemission spectroscopy(ARPES) was claimed to be caused by a tight-binding electron–phonon(e–ph) coupling in the previous theoretical studies. However, we numerically find that the e–ph coupling effect in this approach is too weak to account for the ARPES data. The former agreement between this approach and the ARPES data is due to an enlargement of the coupling constant by almost four times.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11472243,11302189,and 11321202)the Doctoral Fund of Ministry of Education of China(Grant No.20130101120175)+1 种基金the Zhejiang Provincial Qianjiang Talent Program,China(Grant No.QJD1202012)the Educational Commission of Zhejiang Province,China(Grant No.Y201223476)
文摘We investigate the effects of pre-stress and surface tension on the electron–acoustic phonon scattering rate and the mobility of rectangular silicon nanowires. With the elastic theory and the interaction Hamiltonian for the deformation potential, which considers both the surface energy and the acoustoelastic effects, the phonon dispersion relation for a stressed nanowire under spatial confinement is derived. The subsequent analysis indicates that both surface tension and pre-stress can dramatically change the electron–acoustic phonon interaction. Under a negative(positive) surface tension and a tensile(compressive) pre-stress, the electron mobility is reduced(enhanced) due to the decrease(increase) of the phonon energy as well as the deformation-potential scattering rate. This study suggests an alternative approach based on the strain engineering to tune the speed and the drive current of low-dimensional electronic devices.
基金the Doctoral Research Fund of Southwest University of Science and Technology(Grant No.21zx7113)the National Natural Science Foundation of China(Grant Nos.11804284 and 11802280)。
文摘The search for new two-dimensional(2 D)harvesting materials that directly convert(waste)heat into electricity has received increasing attention.In this work,thermoelectric(TE)properties of monolayer square-Au_(2)S are accurately predicted using a parameter-free ab initio Boltzmann transport formalism with fully considering the spin–orbit coupling(SOC),electron–phonon interactions(EPIs),and phonon–phonon scattering.It is found that the square-Au_(2)S monolayer is a promising room-temperature TE material with an n-type(p-type)figure of merit ZT=2.2(1.5)and an unexpected high n-type ZT=3.8 can be obtained at 600 K.The excellent TE performance of monolayer square-Au_(2)S can be attributed to the ultralow lattice thermal conductivity originating from the strong anharmonic phonon scattering and high power factor due to the highly dispersive band edges around the Fermi level.Additionally,our analyses demonstrate that the explicit treatments of EPIs and SOC are highly important in predicting the TE properties of monolayer square-Au_(2)S.The present findings will stimulate further the experimental fabrication of monolayer square-Au_(2)S-based TE materials and offer an in-depth insight into the effect of SOC and EPIs on TE transport properties.
文摘The unexplored terahertz (THz) region involves important phenomena of both fundamental and applied natures. Examples include phonon interactions, rotational transitions and intermolecular dynamics. Frequency tunable high power THz wave generation has been successfully achieved utilizing lattice resonance of LiNbO3 and GaP crystals, respectively. Semiconductor devices utilizing electron tunneling effect have also been developed.
文摘We describe a scheme for universal quantum computation with Majorana fermions. We investigate two possible dissipative couplings of Majorana fermions to external systems, including metallic leads and local phonons. While the dissipation when coupling to metallic leads to uninteresting states for the Majorana fermions, we show that coupling the Majorana fermions to local phonons allows to generate arbitrary dissipations and therefore universal quantum operations on a single QuBit that can be enhanced by additional two-QuBit operations.
基金Project supported by the National Natural Science Foundation of China (Grant No 10974058)the Shanghai Natural Science Foundation of China (Grant No 09ZR1421400)+1 种基金Science and Technology Program of Shanghai Maritime University (Grant No2008475)Postdoctoral Science Foundation of Jiangsu Province of China (Grant No 0802008C)
文摘The nonequilibrium Kondo effect is studied in a molecule quantum dot coupled asymmetrically to two ferromagnetic electrodes by employing the nonequilibrium Green function technique. The current-induced deformation of the molecule is taken into account, modeled as interactions with a phonon system, and phonon-assisted Kondo satellites arise on both sides of the usual main Kondo peak. In the antiparallel electrode configuration, the Kondo satellites can be split only for the asymmetric dot-lead couplings, distinguished from the parallel configuration where splitting also exists, even though it is for symmetric case. We also analyze how to compensate the splitting and restore the suppressed zero-bias Kondo resonance. It is shown that one can change the TMR ratio significantly from a negative dip to a positive peak only by slightly modulating a local external magnetic field, whose value is greatly dependent on the electron-phonon coupling strength.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0403501)the National Natural Science Foundation of China(Grant No.21873033)the Program for HUST Academic Frontier Youth Team。
文摘We show that a current-carrying coherent electron conductor can be treated as an effective bosonic energy reservoir involving different types of electron–hole pair excitations.For weak electron–boson coupling,hybrid energy transport between nonequilibrium electrons and bosons can be described by a Landauer-like formula.This allows for unified account of a variety of heat transport problems in hybrid electron–boson systems.As applications,we study the non-reciprocal heat transport between electrons and bosons,thermoelectric current from a cold-spot,and electronic cooling of the bosons.Our unified framework provides an intuitive way of understanding hybrid energy transport between electrons and bosons in their weak coupling limit.It opens the way of nonequilibrium reservoir engineering for efficient energy control between different quasi-particles at the nanoscale.
基金supported by the Science and Technology Development Plan of Qinhuangdao(No.201101A027)
文摘The temperature and LO phonon effects of the bipolaron in polar semiconductor quantum dots (QDs) are studied by using the Tokuda modified linear-combination operator method and the Lee-Low-Pines variational method. The expressions for the mean number ofLO phonons and the effective mass of the bipolaron are derived. Numerical results show that the mean number of LO phonons of the bipolaron decreases with increasing the temperature and the relative distance r between two electrons, but increases with increasing the electron-phonon coupling strength a The effective mass of the bipolaron M* increases rapidly with increasing the relative distance r between two electrons when r is smaller, and it reaches a maximum at r ≈ 4.05rp, while after that, 34* decreases slowly with increasing r. The effective mass of the bipolaron M' decreases with increasing the temperature. The electron-phonon coupling strength a markedly influences the changes of mean number of LO phonons and the effective mass M* with the relative distance r and the temperature parameter y.
基金This work is supported by the National Nature Science Foundation of China!(No. 69678003)
文摘A theory of ultrasonic generation via direct interaction of transverse optic (TO) phonons with photons in anharmonic lattice of ionic crystals is presented. There are two methods of supplying light energy for the excitation of TO lattice wave as a high frequency ultrasound: (A) incident light comes from the source outside the cavity? fulfilled with ionic crystal medium, (B) photon mode of the cavity possesses the gain of amplification by stimulated radiation of active atoms doping in the medium. More attention is drawn to the case (B). The working system of case (B), as a mixture of lasing action and ultrasonic generation, has the threshold phenomena like usual laser. And the linear stability analysis shows that the nonlineax phonon-photon coupling and the interaction among phonons themselves, both of which reflect the anharmonicity of lattice vibration, are necessary to the stable ultrasonic output. So this laser-ultrasonic generation mixture would be also a measure to investigate the lattice-dynamic nonlinearity and correlated electromagnetic properties of ionic crystals.
基金supported by the National Science Foundation of China(Nos.51103054 and 91233113)the Ministry of Science and Technology of China(No.2013CB834705)the PCSIRT(No.20921003)
文摘We investigate terahertz radiation (T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exeiton transferring to the vibrational excited state via electron-phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simDle device at room temperature.
基金supported in part by the National Natural Science Foundation of China (Grant Nos. 11890703, and 12075168)the Science and Technology Commission of Shanghai Municipality (Grant Nos. 19ZR1478600, and 21JC1405600)+3 种基金the Fundamental Research Funds for the Central Universities (Grant No. 22120220060)supported in part by the RIE2020 Advanced Manufacturing and Engineering (AME) Programmatic (Grant No. A1898b0043)Singapore Aerospace Programme Cycle 15 (Grant No. M2115a0092)supported by the Singapore Ministry of Education AcRF Tier 2 (Grant No. T2EP50220-0026)。
文摘Recently, emerging phonon phenomena have been discovered and rapidly developed, which have become an active hot research topic. In this review article, we present state-of-the-art advances in several fascinating phonon transport phenomena. First, we summarize the recent progress on the wave nature of phonons, including phonon coherence and its effects on thermal conductivity and the topological properties of phonons. Then, we discuss the particle nature of phonons, including the weak coupling of phonons and the high-order phonon anharmonicity. Finally, we present the summary and a brief outlook. This review presents the advanced understanding of some emerging phonon phenomena in solid materials, which provides new opportunities for further advancement in a wide variety of applications.
文摘The investigation of the polar optical vibration modes in semiconductor superlattices by different models are reviewed. It is emphasized that the simple analytic representations of the lattice modes calculated with the dipole oscillator model have introduced the double boundary condition that both the electrostatic potential and optical displacement vanish at the interfaces and have found wide acceptance. They have been referred to as the Huang Zhu model. It is pointed out that its improved simulation version is essentially the dielectric continuum model taking account of phonon dispersion and subject to the double boundary condition.