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Electron-phonon Interaction in Small Systems

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Chinese Physics Letters 1996年第12期13卷 919-922页

作者： WANG Zhong-he ZHANG Cun-zhou ZHANG Guang-yin Deptatment of Physics Nankai UniversityTianjin 300071

The effects of electron-phonon interaction have to be taken into account for the physical process in a small system of condensed matters.The electron-phonon interaction in a I-D finite lattice system has been analyzed.The relation between the electron-phonon interaction and the symmetric properties of electronic states and phonons are considered,the transition probabilities are discussed.

关键词： phonon interaction system

Macroscopic Quantum Superposition States in a Model of Photon-Supersonic phonon Interaction

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Chinese Physics Letters 2000年第7期17卷 504-506页

作者：柴金华王延帮路轶群 Anhui Institute of Optics and Fine Mechanics Chinese Academy of SciencesHefei 230031 Institute of Physics Chinese Academy of SciencesBeijing 100080

A model of photon-hypersonic phonon interaction is proposed. The evolution of macroscopic quantum superpo sition states is analyzed, including the wave function and number distribution. It is shown that a superpositio... 详细信息

关键词： phonon superposition quantum

Accurate and effective computation of the multi-phonon nonradiative transition

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Science China(Physics,Mechanics & Astronomy) 2020年第11期63卷 128-128页

作者： Su-Huai Wei Beijing Computational Science Research Center Beijing 100193China

Nonradiative carrier recombination at a defect or impurity level can reduce the collection of photo-generated carriers and suppress luminescence.Therefore,understanding the underlying mechanism and providing an accurate theoretical prediction of the carrier capture rate(CCR)of a defect in a semiconductor are important for both semiconductor physics and device engineering[1-5].

关键词： defect phonon radiative

Electron–phonon coupling in topological insulator Bi_2Se_3 thin films with different substrates

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Chinese Optics Letters 2019年第2期17卷 21-24页

作者：江天苗润林赵杰许中杰周侗韦可尤洁郑鑫王振宇程湘爱 College of Advanced Interdisciplinary Studies National University of Defense Technology State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Interdisciplinary Center of Quantum Information National University of Defense Technology National Institute of Defense Technology Innovation Academy of Military Sciences PLA China

Broadband transient reflectivity traces were measured for Bi_2 Se_3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi_2 Se_3 and qualitatively located it by properly analyzing the traces acquired at different probe wavelengths. Referring to the band structure of Bi_2 Se_3, the relaxation mechanisms for photo-excited electrons with different energies are also revealed and studied. Our results show a second rise of the transient reflection signal at the time scale of several picoseconds. The types of substrate can also significantly affect the dynamics of the rising signal. This phenomenon is attributed to the effect of lattice heating and coherent phonon processes. The mechanism study in this work will benefit the fabrication of high-performance photonic devices based on topological insulators.

关键词： phonon coupling insulator films

Elastic Constants and phonon Dispersion Curves of Tetragonal La_(2)CuO_(4) Single Crystal

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Chinese Physics Letters 1991年第4期8卷 195-198页

作者： MU Yaoming TAO Ruibao Department of Physics Fudan UniversityShanghai 200433 Center of Theoretical Physics(CCAST World Laboratory) Beijing 100080

The elastic constants and phonon dispersion curves of tetragonal La_(2)CuO_(4) single crystal are calculated with rigid-ion model.We obtain rather good agreement between the computed and measured elastic constants.The calculated phonon dispersion curves exhibit a rather conventional behavior except the anomaly of aΣ_(4),symmetry TO mode atΓ-X direction.

关键词： phonon dispersion Dispersion

Inherent Anharmonicity of Harmonic Solids

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Research 2022年第3期2022卷 409-419页

作者： Matthias T.Agne Shashwat Anand G.Jeffrey Snyder Department Materials Science and Engineering Northwestern UniversityEvanstonILUSA

Atomic vibrations,in the form of phonons,are foundational in describing the thermal behavior of materials.The possible frequencies of phonons in materials are governed by the complex bonding between atoms,which is physically represented by a spring-mass model that can account for interactions(spring forces)between the atoms(masses).The lowest-order,harmonic,approximation only considers linear forces between atoms and is thought incapable of explaining phenomena like thermal expansion and thermal conductivity,which are attributed to nonlinear,anharmonic,interactions.Here,we show that the kinetic energy of atoms in a solid produces a pressure much like the kinetic energy of atoms in a gas does.This vibrational or phonon pressure naturally increases with temperature,as it does in a gas and therefore results in a thermal expansion.Because thermal expansion thermodynamically defines a Grüneisen parameterγ,which is a typical metric of anharmonicity,we show that even a harmonic solid will necessarily have some anharmonicity.A consequence of this phonon pressure model is a harmonic estimation of the Grüneisen parameter asγ≈(3/2)(3−4x^(2))/(1+2x^(2)),where x=vt/vl is the ratio of the transverse and longitudinal speeds of sound.We demonstrate the immediate utility of this model by developing a high-throughput harmonic estimate of lattice thermal conductivity that is comparable to other state-of-the-art estimations.By linking harmonic and anharmonic properties explicitly,this study provokes new ideas about the fundamental nature of anharmonicity,while also providing a basis for new material engineering design metrics.

关键词： harmonic phonon linking

Optical Interface phonon in Graded Quantum Well Structures

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Chinese Physics Letters 1994年第6期11卷 349-352页

作者： ZHU Jialin DUAN Wenhui GU Binglin Department of Physics Tsinghua UniversityBeijing 100084 Central Iron and Steel Research Institute Beijing 100081

The behaviour of optical interface phonon is investigated first for the graded quantum well of Ga_(l-x)Al_(x)As in the dielectric continuum model.It is found that the behaviour of interface phonon modes is quite different from that in square quantum well structure.The dispersions of the interface modes are sensitive to the gradient of the graded quantum well structure,and the symmetry of modes can be changed greatly,which is important for phonon-related phenomena.

关键词： structure model phonon

Tailored morphology and highly enhanced phonon transport in polymer fibers:a multiscale computational framework

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npj Computational Materials 2019年第1期5卷 36-47页

作者： Shangchao Lin Zhuangli Cai Yang Wang Lingling Zhao Chenxi Zhai Institute of Engineering Thermophysics School of Mechanical and Power EngineeringShanghai Jiao Tong UniversityShanghai 200240China Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjingJiangsu 210096China Department of Mechanical Engineering FAMU-FSU College of EngineeringFlorida State UniversityTallahasseeFL 32310USA

Although tremendous efforts have been devoted to enhance thermal conductivity in polymer fibers,correlation between the thermal-drawing conditions and the resulting chain alignment,crystallinity,and phonon transport properties have remained obscure.Using a carefully trained coarse-grained force field,we systematically interrogate the thermal-drawing conditions of bulk polyethylene samples using large-scale molecular dynamics simulations.An optimal combination of moderate drawing temperature and strain rate is found to achieve highest degrees of chain alignment,crystallinity,and the resulting thermal conductivity.Such combination is rationalized by competing effects in viscoelastic relaxation and condensed to the Deborah number,a predictive metric for the thermal-drawing protocols,showing a delicate balance between stress localizations and chain diffusions.Upon tensile deformation,the thermal conductivity of amorphous polyethylene is enhanced to 80% of the theoretical limit,that is,its pure crystalline counterpart.An effective-medium-theory model,based on the serial-parallel heat conducting nature of semicrystalline polymers,is developed here to predict the impacts from both chain alignment and crystallinity on thermal conductivity.The enhancement in thermal conductivity is mainly attributed to the increases in the intrinsic phonon mean free path and the longitudinal group velocity.This work provides fundamental insights into the polymer thermal-drawing process and establishes a complete process–structure–property relationship for enhanced phonon transport in all-organic electronic devices and efficiency of polymeric heat dissipaters.

关键词： fibers transport phonon

Observation of mechanical bound states in the continuum in an optomechanical microresonator

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Light(Science & Applications) 2022年第12期11卷 2931-2938页

作者： Yue Yu Xiang Xi Xiankai Sun Department of Electronic Engineering The Chinese University of Hong KongShatinNew TerritoriesHong Kong SARChina

Bound states in the continuum(BICs)are a type of waves that are perfectly confined in the continuous spectrum of radiating waves without interaction with them.Here,we fabricated,with CMOS-compatible processes on a silicon chip,a wheel-shaped optomechanical microresonator,in which we experimentally observed the BIC in the micromechanical domain.The BIC results from destructive interference between two dissipative mechanical modes of the microresonator under broken azimuthal symmetry.Such BICs can be obtained from devices with large and robust supporting structures with variable sizes,which substantially reduces fabrication difficulty and allows for versatile application environments.Our results open a new way of phonon trapping in micromechanical structures with dissipation channels,and produce long phonon lifetimes that are desired in many mechanical applications such as mechanical oscillators,sensors,and quantum information processors.

关键词： phonon continuum states