Structurally Flexible 2D Spacer for Suppressing the Electron-Phonon Coupling Induced Non-Radiative Decay in Perovskite Solar Cells

This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker electron-phonon coupling in perovskite has been achieved by introducing the structurally soft cyclohexane methylamine(CMA^(+))cation,which could serve as a damper to alleviate the mechanical stress caused by lattice oscillations,compared to the rigid phenethyl methylamine(PEA^(+))analog.It demonstrates a significantly lower non-radiative recombination rate,even though the two types of bulky cations have similar chemical passivation effects on perovskite,which might be explained by the suppressed carrier capture process and improved lattice geometry relaxation.The resulting PSCs achieve an exceptional power conversion efficiency(PCE)of 25.5%with a record-high opencircuit voltage(V_(OC))of 1.20 V for narrow bandgap perovskite(FAPbI_(3)).The established correlations between electron-phonon coupling and non-radiative decay provide design and screening criteria for more effective passivators for highly efficient PSCs approaching the Shockley-Queisser limit.

Measurements of electron-phonon coupling factor and interfacial thermal resistance of metallic nano-films using a transient thermoreflectance technique

Using a transient thermoreflectance （TTR） technique, several Au films with different thicknesses on glass and SiC substrates are measured for thermal characterization of metMlic nano-films, including the electron phonon coupling factor G, interfazial thermal resistance R, and thermal conductivity Ks of the substrate. The rear heating-front detecting （RF） method is used to ensure the femtosecond temporal resolution. An intense laser beam is focused on the rear surface to heat the film, and another weak laser beam is focused on the very spot of the front surface to detect the change in the electron temperature. By varying the optical path delay between the two beams, a complete electron temperature profile can be scanned. Different from the normally used single-layer model, the double-layer model involving interfaciM thermal resistance is studied here. The electron temperature cooling profile can be affected by the electron energy transfer into the substrate or the electron-phonon interactions in the metallic films. For multiple-target optimization, the genetic algorithm （GA） is used to obtain both G and R. The experimental result gives a deep understanding of the mechanism of ultra-fast heat transfer in metals.

A novel electron-phonon coupling thermoelasticity with Burgers electronic heat transfer

The electron-phonon interaction can reveal the microscopic mechanism of heat transfer in metals.The two-step heat conduction considering electron-phonon interaction has become an effective theoretical model for extreme environments,such as micro-scale and ultrafast processes.In this work,the two-step heat transfer model is further extended by considering the Burgers heat conduction model with the secondorder heat flux rate for electrons.Then,a novel generalized electron-phonon coupling thermoelasticity is proposed with the Burgers electronic heat transfer.Then,the problem of one-dimensional semi-infinite copper strip subject to a thermal shock at one side is studied by the Burgers two-step(BTS)model.The thermoelastic analytical solutions are systematically derived in the Laplace domain,and the numerical Laplace inversion method is adopted to obtain the transient responses.The new model is compared with the parabolic two-step(PTS)model and the hyperbolic two-step(HTS)model.The results show that in ultrafast heating,the BTS model has the same wave front jump as the HTS model.The present model has the faster wave speed,and predicts the bigger disturbed regions than the HTS model.More deeply,all two-step models also have the faster wave speeds than one-step models.This work may benefit the theoretical modeling of ultrafast heating of metals.

Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering

Electron-phonon coupling （EPC） in cuprate and iron-based superconducting systems, as revealed by Raman scat- tering, is briefly reviewed. We introduce how to extract the coupling information through phonon lineshape. Then we discuss the strength of EPC in different high-temperature superconductor （HTSC） systems and possible factors affecting the strength. A comparative study between Raman phonon theories and experiments allows us to gain insight into some crucial electronic properties, especially superconductivity. Finally, we summarize and compare EPC in the two existing HTSC systems, and discuss what role it may play in the HTSC.

Comment on “Exact Solution of Persistent Currents in One-Dimensional Mesoscopic Rings with Consideration of Electron-Phonon Coupling”

The effect of electron-phonon coupling on persistent currents in one-dimensional rings is an interesting and not completely solved problem.Reference 1 claims that the exact solution of persistent current in one-dimensiona.1 ring with consideration of electron-phonon coupling has been found out,and the effects of persistent current and the interaction between electron and phonon can be considered separately.As well-known,in the quantum mechanics and the solid state physics only a few of equations can be exactly solved,so it is important to check whether the results of Ref.1 are true.In this letter we point out that the results of Ref.1 are not true since there is a mistake in their calculation.

On the Eigenvalue Problem in One-Dimensional Mesoscopic Rings with Electron-Phonon Coupling

By invoking the concept of displaced number state in quantum optics,the complete eigen-states in one-dimensional mesoscopic rings with electron-phonon coupling are abtained and the eignevalues followed.It is shown that the eigenvalues and persistent current depend on both coupling strength and phonon number.

Purity-dependent Lorenz number,electron hydrodynamics and electron-phonon coupling in WTe_(2)

We present a study of electrical and thermal transport in Weyl semimetal WTe_(2)down to 0.3 K.The Wiedemann-Franz law holds below 2 K and a downward deviation starts above.The deviation is more pronounced in cleaner samples,as expected in the hydrodynamic picture of electronic transport,where a fraction of electron-electron collisions conserve momentum.Phonons are the dominant heat carriers and their mean-free-path does not display a Knudsen minimum.This is presumably a consequence of weak anharmonicity,as indicated by the temperature dependence of the specific heat.Frequent momentum exchange between phonons and electrons leads to quantum oscillations of the phononic thermal conductivity.Bloch-Grüneisen picture of electron-phonon scattering breaks down at low temperature when Umklapp ph-ph collisions cease to be a sink for electronic flow of momentum.Comparison with semi-metallic Sb shows that normal ph-ph collisions are amplified by anharmonicity.In both semimetals,at cryogenic temperature,e-ph collisions degrade the phononic flow of energy but not the electronic flow of momentum.

Defects‑Rich Heterostructures Trigger Strong Polarization Coupling in Sulfides/Carbon Composites with Robust Electromagnetic Wave Absorption

Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.

Correlation-enhanced electron-phonon coupling for accurate evaluation of the superconducting transition temperature in bulk FeSe

It has been widely recognized that,based on standard density functional theory calculations of the electron-phonon coupling,the superconducting transition temperature(T_(c))in bulk FeSe is exceptionally low(almost 0 K)within the Bardeen-Cooper-Schrieffer formalism.Yet the experimentally observed T_(c)is much higher(∼10 K),and the underlying physical origin remains to be fully explored,especially at the quantitative level.Here we present the first accurate determination of T_(c)in FeSe where the correlation-enhanced electron-phonon coupling is treated within first-principles dynamical mean-field theory.Our studies treat both the multiple electronic bands across the Fermi level and phononic bands,and reveal that all the optical phonon modes are effectively coupled with the conduction electrons,including the important contributions of a single breathing mode as established by previ-ous experiments.Accordingly,each of those phonon modes contributes pronouncedly to the electron pairing,and the resultant T_(c)is drastically enhanced to the experimentally observed range.The approach developed here should be broadly applicable to other superconducting systems where correlation-enhanced electron-phonon coupling plays an important role.

Calculating electron-phonon coupling matrix: Theory introduction,code development and preliminary application

Electron-phonon coupling(EPC) in bulk materials is an important effect in multifarious physical and chemical phenomena. It is the key to explaining the mechanisms for superconductivity, electronic transport, etc. The EPC matrix describes the coupling of the electronic eigenstates of the studied system under the perturbation of phonons. Although the EPC matrix is closely relevant to many fundamental physicochemical properties, it remains a challenge to calculate the EPC matrix precisely due to the high computational cost. In recent years, Giustino et al. developed the EPW method on open-source ab-initio software Quantum Espresso, which uses Wannier functions(WFs) to calculate EPC matrix. However, due to the limitation of their implementation,it is not possible yet to calculate the EPC matrix under some important computational conditions, e.g., for DFT+U and HSE calculation. Given the importance of these computational conditions(e.g., for transition metal oxides), we have developed our own implementation of EPC matrix calculation based on the domestic ab-initio software PWmat. Our code allows the DFT+U and HSE correction, so we can get a more accurate EPC matrix in the related problems. In this article, we will first review the formulae and elucidate how to calculate the EPC matrix by constructing WFs. Then we will introduce our code along with its workflow on PWmat and present our test results of two classical semiconductor systems Al As and Si, showing consistency with EPW. Next, the EPC matrix of Li Co O_(2), a classical cathode material for lithium-ion batteries, is calculated using different exchange correlation(XC) functionals including LDA, PBE, DFT+U and HSE. A comparison is provided for the related EPC matrix. It shows there could be a significant difference for the EPC matrix elements due to the use of different XC functionals.Our implementation thus opens the way for fast calculation of EPC for the important class of materials, like the transition metal oxides.

Detection of electron-phonon coupling in two-dimensional materials by light scattering

Electron-phonon coupling affects the properties of two-dimensional(2D)materials significantly,leading to a series of novel phenomena.Inelastic light scattering provides a powerful experimental tool to explore electron-phonon interaction in 2D materials.This review gives an overview of the basic theory and experimental advances of electron-phonon coupling in 2D materials detected by Raman and Brillouin scattering,respectively.In the Raman scattering part,we review Raman spectroscopy studies of electron-phonon coupling in graphene,transition metal disulfide compounds,van der Waals heterostructures,strongly correlated systems,and 2D magnetic materials.In the Brillouin scattering part,we extensively introduce Brillouin spectroscopy in non-van der Waals 2D structures,including temperature sensors for phonons and magnons,interfacial Dzyaloshinsky-Moriya interaction and spin torque in multilayer magnetic structures,as well as exciton-polariton in semiconductor quantum well.

Thermoelectric transport properties in chalcogenides ZnX (X=S, Se): From the role of electron-phonon couplings

Electron-phonon coupling(EPC)is a key factor for thermoelectric properties of materials.In this paper,the thermoelectric properties of zinc-blende chalcogenides(p-type)ZnS and ZnSe have been studied through full evaluation of EPC from first-principles,including the influences on both electrical and thermal transport.We find that the polar longitudinal optical phonon scattering is the dominant mechanism for electrical transport.Due to the triple degeneracy near the valence band maximum,the inter-band scattering also has detrimental contributions to the electrical conductivities.For phonon transport,it shows that the lattice thermal conductivity can be reduced by the electron-phonon scattering significantly at high carrier concentrations(e.g.,at 300 K with 10^(21) cm^(3) of hole,the reduction is-24.9%for ZnS and-28.4%for ZnSe,respectively).Finally,the p-type thermoelectric figure of merit(ZT)of two systems have been obtained,which are 0.129 for ZnS and 0.141 for ZnSe,at 700 K with their respective optimal hole concentrations.Our work provides a complete and in-depth study of thermoelectric properties in chalcogenides ZnX from the role of EPC.The results suggest EPC plays an important role on the thermoelectric properties and thus full evaluation of EPC is necessary especially for polar materials.

Effects of electron-phonon coupling on the phonon transport properties of the Weyl semimetals NbAs and TaAs:A comparative study

It has now become recognized that the electron-phonon coupling(EPC)may play an important role in governing the phonon transport,especially for metallic and semiconducting systems at high carrier concentration.Here we focus on the Weyl semimetals TaAs and NbAs and give a comparative study on their phonon transport properties by explicitly including the EPC in first-principles calculations.It is found that the lattice thermal conductivities of both systems are significantly reduced by the EPC,which is more pronounced for the TaAs compared with the NbAs at the same carrier concentration.Detailed analysis indicates that the TaAs exhibits smaller EPC phonon relaxation time,as characterized by stronger EPC strength which is associated with larger deformation potential constant and Born effective charge.Moreover,we see that the TaAs exhibits obviously larger overlap between the EPC relaxation time and that from intrinsic phonon-phonon scattering,which could further reduce the lattice thermal conduc-tivity.Our work not only highlights the vital importance of EPC in accurately predicting the phonon transport behaviors,but also offers a simple alternative to evaluate the EPC strength of various material systems.

Influence of water coupling coefficient on the blasting effect of red sandstone specimens

This study investigates the impact of different water coupling coefficients on the blasting effect of red sandstone.The analysis is based on the theories of detonation wave and elastic wave,focusing on the variation in wall pressure of the blasting holes.Using DDNP explosive as the explosive load,blasting tests were conducted on red sandstone specimens with four different water coupling coefficients:1.20,1.33,1.50,and 2.00.The study examines the morphologies of the rock specimens after blasting under these different water coupling coefficients.Additionally,the fractal dimensions of the surface cracks resulting from the blasting were calculated to provide a quantitative evaluation of the extent of rock damage.CT scanning and 3D reconstruction were performed on the post-blasting specimens to visually depict the extent of damage and fractures within the rock.Additionally,the volume fractal dimension and damage degree of the post-blasting specimens are calculated.The findings are then combined with numerical simulation to facilitate auxiliary analysis.The results demonstrate that an increase in the water coupling coefficient leads to a reduction in the peak pressure on the hole wall and the crushing zone,enabling more of the explosion energy to be utilized for crack propagation following the explosion.The specimens exhibited distinct failure patterns,resulting in corresponding changes in fractal dimensions.The simulated pore wall pressure–time curve validated the derived theoretical results,whereas the stress cloud map and explosion energy-time curve demonstrated the buffering effect of the water medium.As the water coupling coefficient increases,the buffering effect of the water medium becomes increasingly prominent.

Strong coupling and catenary field enhancement in the hybrid plasmonic metamaterial cavity and TMDC monolayers

Strong coupling between resonantly matched surface plasmons of metals and excitons of quantum emitters results in the formation of new plasmon-exciton hybridized energy states.In plasmon-exciton strong coupling,plasmonic nanocavities play a significant role due to their ability to confine light in an ultrasmall volume.Additionally,two-dimensional transition metal dichalcogenides(TMDCs) have a significant exciton binding energy and remain stable at ambient conditions,making them an excellent alternative for investigating light-matter interactions.As a result,strong plasmon-exciton coupling has been reported by introducing a single metallic cavity.However,single nanoparticles have lower spatial confinement of electromagnetic fields and limited tunability to match the excitonic resonance.Here,we introduce the concept of catenary-shaped optical fields induced by plasmonic metamaterial cavities to scale the strength of plasmon-exciton coupling.The demonstrated plasmon modes of metallic metamaterial cavities offer high confinement and tunability and can match with the excitons of TMDCs to exhibit a strong coupling regime by tuning either the size of the cavity gap or thickness.The calculated Rabi splitting of Au-MoSe_2 and Au-WSe_2 heterostructures strongly depends on the catenary-like field enhancement induced by the Au cavity,resulting in room-temperature Rabi splitting ranging between 77.86 and 320 me V.These plasmonic metamaterial cavities can pave the way for manipulating excitons in TMDCs and operating active nanophotonic devices at ambient temperature.

Icariin accelerates bone regeneration by inducing osteogenesisangiogenesis coupling in rats with type 1 diabetes mellitus

BACKGROUND Icariin(ICA),a natural flavonoid compound monomer,has multiple pharmacological activities.However,its effect on bone defect in the context of type 1 diabetes mellitus(T1DM)has not yet been examined.AIM To explore the role and potential mechanism of ICA on bone defect in the context of T1DM.METHODS The effects of ICA on osteogenesis and angiogenesis were evaluated by alkaline phosphatase staining,alizarin red S staining,quantitative real-time polymerase chain reaction,Western blot,and immunofluorescence.Angiogenesis-related assays were conducted to investigate the relationship between osteogenesis and angiogenesis.A bone defect model was established in T1DM rats.The model rats were then treated with ICA or placebo and micron-scale computed tomography,histomorphometry,histology,and sequential fluorescent labeling were used to evaluate the effect of ICA on bone formation in the defect area.RESULTS ICA promoted bone marrow mesenchymal stem cell(BMSC)proliferation and osteogenic differentiation.The ICA treated-BMSCs showed higher expression levels of osteogenesis-related markers(alkaline phosphatase and osteocalcin)and angiogenesis-related markers(vascular endothelial growth factor A and platelet endothelial cell adhesion molecule 1)compared to the untreated group.ICA was also found to induce osteogenesis-angiogenesis coupling of BMSCs.In the bone defect model T1DM rats,ICA facilitated bone formation and CD31hiEMCNhi type H-positive capillary formation.Lastly,ICA effectively accelerated the rate of bone formation in the defect area.CONCLUSION ICA was able to accelerate bone regeneration in a T1DM rat model by inducing osteogenesis-angiogenesis coupling of BMSCs.

Rheological properties and concentration evolution of thickened tailings under the coupling effect of compression and shear

Cemented paste backfill(CPB)is a key technology for green mining in metal mines,in which tailings thickening comprises the primary link of CPB technology.However,difficult flocculation and substandard concentrations of thickened tailings often occur.The rheological properties and concentration evolution in the thickened tailings remain unclear.Moreover,traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties.An experiment of flocculation condition optimization based on the Box-Behnken design(BBD)was performed in the study,and the two response values were investigated:concentration and the mean weighted chord length(MWCL)of flocs.Thus,optimal flocculation conditions were obtained.In addition,the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear,compression,and compression-shear coupling experimental conditions were tested and compared.The results show that the shear yield stress under compression and compression-shear coupling increases with the growth of compressive yield stress,while the shear yield stress increases slightly under shear.The order of shear yield stress from low to high under different thickening conditions is shear,compression,and compression-shear coupling.Under compression and compression-shear coupling,the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases,while concentration increases slightly under shear.The order of concentration from low to high under different thickening conditions is shear,compression,and compression-shear coupling.Finally,the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.

Metal–Organic Gel Leading to Customized Magnetic‑Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances

Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.

Algorithm Selection Method Based on Coupling Strength for Partitioned Analysis of Structure-Piezoelectric-Circuit Coupling

In this study, we propose an algorithm selection method based on coupling strength for the partitioned analysis ofstructure-piezoelectric-circuit coupling, which includes two types of coupling or inverse and direct piezoelectriccoupling and direct piezoelectric and circuit coupling. In the proposed method, implicit and explicit formulationsare used for strong and weak coupling, respectively. Three feasible partitioned algorithms are generated, namely(1) a strongly coupled algorithm that uses a fully implicit formulation for both types of coupling, (2) a weaklycoupled algorithm that uses a fully explicit formulation for both types of coupling, and (3) a partially stronglycoupled and partially weakly coupled algorithm that uses an implicit formulation and an explicit formulation forthe two types of coupling, respectively.Numerical examples using a piezoelectric energy harvester,which is a typicalstructure-piezoelectric-circuit coupling problem, demonstrate that the proposed method selects the most costeffectivealgorithm.

Versatile band structure and electron-phonon coupling in layered PtSe_(2) with strong interlayer interaction

The large tunability in the band structure is ubiquitous in two-dimensional(2D)materials,and PtSe_(2) is not an exception,which has attracted considerable attention in electronic and optoelectronic applications due to its high carrier mobility and long-term airstability.Such dimensional dependent properties are closely related to the evolution of electronic band structures.Critical points(CPs),the extrema or saddle points of electronic bands,are the cornerstone of condensed-matter physics and fundamentally determine the optical and transport phenomena of the layered PtSe_(2).Here,we have experimentally revealed the detailed electronic structures in layered PtSe_(2),including the CPs in the Brillouin zones(BZs),by means of reflection contrast spectroscopy and spectroscopic ellipsometry(SE).There are three critical points in the BZs attributed to the excitonic transition,quasi-particle band gap,and the band nesting effect related transition,respectively.Three CPs show red-shifting trends with increasing layer number under the mechanism of strong interlayer coupling.We have further revealed the electron–phonon(e–ph)interaction in such layered material,utilizing temperature-dependent absorbance spectroscopy.The strength of e–ph interaction and the average phonon energy also decline with the increasement of layer number.Our findings give a deep understanding to the physics of the layer-dependent evolution of the electronic structure of PtSe_(2),potentially leading to applications in optoelectronics and electronic devices.