Journal articles on the topic 'Transport des phonons'
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1
Liu, Yizhou, Yong Xu, and Wenhui Duan. "Three-Dimensional Topological States of Phonons with Tunable Pseudospin Physics." Research 2019 (July 31, 2019): 1–8. http://dx.doi.org/10.34133/2019/5173580.
Abstract:
Efficient control of phonons is crucial to energy-information technology, but limited by the lacking of tunable degrees of freedom like charge or spin. Here we suggest to utilize crystalline symmetry-protected pseudospins as new quantum degrees of freedom to manipulate phonons. Remarkably, we reveal a duality between phonon pseudospins and electron spins by presenting Kramers-like degeneracy and pseudospin counterparts of spin-orbit coupling, which lays the foundation for “pseudospin phononics”. Furthermore, we report two types of three-dimensional phononic topological insulators, which give topologically protected, gapless surface states with linear and quadratic band degeneracies, respectively. These topological surface states display unconventional phonon transport behaviors attributed to the unique pseudospin-momentum locking, which are useful for phononic circuits, transistors, antennas, etc. The emerging pseudospin physics offers new opportunities to develop future phononics.
2
Manuel, Cristina, and Laura Tolos. "Transport Properties of Superfluid Phonons in Neutron Stars." Universe 7, no. 3 (March 5, 2021): 59. http://dx.doi.org/10.3390/universe7030059.
Abstract:
We review the effective field theory associated with the superfluid phonons that we use for the study of transport properties in the core of superfluid neutrons stars in their low temperature regime. We then discuss the shear and bulk viscosities together with the thermal conductivity coming from the collisions of superfluid phonons in neutron stars. With regard to shear, bulk, and thermal transport coefficients, the phonon collisional processes are obtained in terms of the equation of state and the superfluid gap. We compare the shear coefficient due to the interaction among superfluid phonons with other dominant processes in neutron stars, such as electron collisions. We also analyze the possible consequences for the r-mode instability in neutron stars. As for the bulk viscosities, we determine that phonon collisions contribute decisively to the bulk viscosities inside neutron stars. For the thermal conductivity resulting from phonon collisions, we find that it is temperature independent well below the transition temperature. We also obtain that the thermal conductivity due to superfluid phonons dominates over the one resulting from electron-muon interactions once phonons are in the hydrodynamic regime. As the phonons couple to the Z electroweak gauge boson, we estimate the associated neutrino emissivity. We also briefly comment on how the superfluid phonon interactions are modified in the presence of a gravitational field or in a moving background.
3
Prasher, Ravi. "Thermal Transport Due to Phonons in Random Nano-particulate Media in the Multiple and Dependent (Correlated) Elastic Scattering Regime." Journal of Heat Transfer 128, no. 7 (January 4, 2006): 627–37. http://dx.doi.org/10.1115/1.2194036.
Abstract:
Effects of multiple and dependent or correlated elastic scattering of phonons due to nanoparticles on thermal transport in random nano-particulate media (random phononic crystals) are investigated in this paper under various approximations. Multiple scattering means that the scattered wave from one particle is incident on another particle to be scattered again. Dependent scattering means far-field interference of the scattered waves due to phase difference, which is ignored in the independent scattering regime. Multiple and dependent scattering effects become important when the interparticle distance is comparable to the wavelength of phonons. Results show that multiple scattering primarily affects the velocity and density of states of phonons and dependent scattering primarily affects the mean free path of phonons. Effects of both multiple and dependent scattering increases with increasing volume fraction of nanoparticles. Modification of these parameters affects the equilibrium phonon intensity and the thermal conductivity of phonons.
4
Bin Mansoor, Saad, and Bekir Sami Yilbas. "Nonequilibrium cross-plane energy transport in aluminum–silicon–aluminum wafer." International Journal of Modern Physics B 29, no. 17 (June 23, 2015): 1550112. http://dx.doi.org/10.1142/s021797921550112x.
Abstract:
Transient phonon transport across cross-planes of aluminum–silicon–aluminum combined films is investigated and the Boltzmann transport equation is incorporated to formulate the energy transport in the combined films. Since electrons and phonons thermally separate in the thin aluminum film during heating, the Boltzmann equation is used separately in the electron and lattice subsystems to account for the energy transport in the aluminum film. Electron–phonon coupling is incorporated for the energy exchange between electron and lattice subsystems in the film. Thermal boundary resistance (TBR) is introduced at the interfaces of the silicon–aluminum films. In order to examine the ballistic contribution of phonons on the phonon intensity distribution in the silicon film, frequency-dependent solution of the Boltzmann equation is used in the silicon film and the film thickness is varied to investigate the size effect on the thermal conductivity in the film. It is found that equivalent equilibrium temperature of phonons remains high at silicon–aluminum interface because of the ballistic contribution of the phonons. Equivalent equilibrium temperature for the electron subsystem becomes higher than that corresponding to phonon temperature at the aluminum–silicon interface.
5
Lax, M., and W. Cai. "EFFECT OF NONEQUILIBRIUM PHONONS ON THE ELECTRON RELAXATION AND TRANSPORT." International Journal of Modern Physics B 06, no. 07 (April 10, 1992): 975–1006. http://dx.doi.org/10.1142/s0217979292000529.
Abstract:
We review the recent theoretical study of the effect of nonequilibrium phonons on hot-carrier relaxation and transport. In a quantum well, the proper treatment of the electron-phonon coupling between electrons confined to two dimensions (2-D) by phonons traveling freely in three dimensions (3D) requires special care because phonon heating produces a bottleneck in the rate of transfer of energy from the carriers to the phonons. Because the carriers interact with phonons primarily when the latter are close to the quantum well, the latter should be described, not by plane waves, but by packets adapted to the shape of the carrier confinement. A quasi-equilibrium technique that retains off-diagonal elements in the phonon wave-vector permits an unrestricted treatment of the density operator equation. That in turn leads to a choice of wave packet that comes from solving the integrodifferential equations rather than by imposition. Moreover, if the carrier distribution is assumed in quasi-equilibrium with a given drift and temperature, the coupled partial differential equations are reduced to coupled ordinary differential equations that can be solved with modest computer power. Comparison with experimental results for steady flow of energy from carriers to phonons, and for time-dependent relaxation yields quantitative agreement.
6
Bao, Bengang, Fei Li, and Xin Zhou. "Characteristics of acoustic phonon transport and thermal conductance in multi-frame graphene nanoribbons." Modern Physics Letters B 32, no. 26 (September 20, 2018): 1850307. http://dx.doi.org/10.1142/s0217984918503074.
Abstract:
Using non-equilibrium Green’s function method and maintaining the zigzag carbon chains unchanged, we investigate the transmission rate of acoustic phonon and the reduced thermal conductance through multi-frame graphene nanoribbons (GNRs). The results show that the reduced thermal conductance approaches [Formula: see text] in the limit [Formula: see text]. Due to the fact that only long wavelength acoustic phonons with zero cutoff frequency are excited at such low temperatures, the scattering influence on the long wavelength acoustic phonons by the multi-frame in GNRs can be ignored and these phonons can go through the scattering region perfectly. As the temperature goes up, the reduced thermal conductance decreases. This is because the high-frequency phonons are excited and these high-frequency phonons are scattered easily by the scattering structures. With the further rise in temperature, acoustic phonon modes with the cutoff frequency greater than zero are excited, which leads to a rapid increase of the reduced thermal conductance. This study shows that changing the frame structure by a small length can lead to a significant change of transmission probability. In the higher frequency region, the transmission spectra display complex peak-dip structures, which results from the fact that in higher frequency region more phonon modes are excited and scattered in the middle scattering region with multi-frames, and the scattering phonons are coupled with the incident phonons, with the increase of the length of frame structure, the scattering of the phonon is also enhanced, which leads to the decrease in the phonon transmission; by changing the frame structure, the parameters can effectively adjust the position of low-frequency phonon transmission valley. The frame structure can induce high-frequency phonon blocking effect and the blocking effect depending on the structure parameter of the frame. When the single frame and double frame GNRs are narrowest, the scattering from low-frequency phonons by the scattering structure is largest, which leads to the fact that the reduced thermal conductance is smallest at low temperatures; however, at high temperature, the reduced thermal conductance is biggest when the single frame and double frame GNRs are narrowest. This is because the scattering from high-frequency phonons by the scattering structure is the smallest. When the length of the frame structure is unchanged, a graphite chain is inserted in which the reduced thermal conductance is always reduced. These results provide an effective theoretical basis for designing the thermal transport quantum devices based on GNRs.
7
Bannov, N. A., V. V. Mitin, and F. T. Vasko. "Modelling of Hot Acoustic Phonon Propagation in Two Dimensional Layers." VLSI Design 6, no. 1-4 (January 1, 1998): 197–200. http://dx.doi.org/10.1155/1998/79658.
Abstract:
The transport of confined acoustic phonons in a flee-standing quantum well has been studied by solving the quantum kinetic equation for phonons. The phonon decay rate has been numerically calculated for GaAs flee-standing quantum well. Phonon interaction with electrons through the deformation potential makes the major contribution to the acoustic phonon decay.
8
Chen, J., and Y. Liu. "Effect of out-of-plane acoustic phonons on the thermal transport properties of graphene." Condensed Matter Physics 26, no. 4 (2023): 43603. http://dx.doi.org/10.5488/cmp.26.43603.
Abstract:
The lattice thermal conductivity of graphene is evaluated using a microscopic model that takes into account the lattice's discrete nature and the phonon dispersion relation within the Brillouin zone. The Boltzmann transport equation is solved iteratively within the framework of three-phonon interactions without taking into account the four-phonon scattering process. The Umklapp and normal collisions are treated rigorously, thereby avoiding relaxation-time and long-wavelength approximations. The mechanisms of the failures of these approximations in predicting the thermal transport properties are discussed. Evaluation of the thermal conductivity is performed at different temperatures and frequencies and in different crystallite sizes. Reasonably good agreement with the experimental data is obtained. The calculation reveals a critical role of out-of-plane acoustic phonons in determining the thermal conductivity. The out-of-plane acoustic phonons contribute greatly and the longitudinal and transverse acoustic phonons make small contributions over a wide range of temperatures and frequencies. The out-of-plane acoustic phonons dominate the thermal conductivity due to their high density of states and restrictions governing the anharmonic phonon scattering. The selection rule severely restricts the phase space for out-of-plane phonon scattering due to reflection symmetry. The optical phonon contribution cannot be neglected at higher temperatures. Both Umklapp and normal processes must be taken into account in order to predict the phonon transport properties accurately.
9
Luckyanova, M. N., J. Mendoza, H. Lu, B. Song, S. Huang, J. Zhou, M. Li, et al. "Phonon localization in heat conduction." Science Advances 4, no. 12 (December 2018): eaat9460. http://dx.doi.org/10.1126/sciadv.aat9460.
Abstract:
Nondiffusive phonon thermal transport, extensively observed in nanostructures, has largely been attributed to classical size effects, ignoring the wave nature of phonons. We report localization behavior in phonon heat conduction due to multiple scattering and interference events of broadband phonons, by measuring the thermal conductivities of GaAs/AlAs superlattices with ErAs nanodots randomly distributed at the interfaces. With an increasing number of superlattice periods, the measured thermal conductivities near room temperature increased and eventually saturated, indicating a transition from ballistic to diffusive transport. In contrast, at cryogenic temperatures the thermal conductivities first increased but then decreased, signaling phonon wave localization, as supported by atomistic Greenșs function simulations. The discovery of phonon localization suggests a new path forward for engineering phonon thermal transport.
10
Prasher, Ravi S. "Mie Scattering Theory for Phonon Transport in Particulate Media." Journal of Heat Transfer 126, no. 5 (October 1, 2004): 793–804. http://dx.doi.org/10.1115/1.1795243.
Abstract:
Scattering theory for the scattering of phonons by particulate scatterers is developed in this paper. Recently the author introduced the generalized equation of phonon radiative transport (GEPRT) in particulate media, which included a phase function to account for the anisotropic scattering of phonons by particulate scatterer. Solution of the GEPRT showed that scattering cross section is different from the thermal transport cross-section. In this paper formulations for the scattering and transport cross section for horizontally shear (SH) wave phonon or transverse wave phonon without mode conversion is developed. The development of the theory of scattering and the transport cross section is exactly analogous to the Mie scattering theory for photon transport in particulate media. Results show that transport cross section is very different from the scattering cross section. The theory of phonon scattering developed in this paper will be useful for the predictive modeling of thermal conductivity of practical systems, such as nanocomposites, nano-micro-particle-laden systems, etc.
11
Kamakura, Yoshinari, Tomofumi Zushi, Takanobu Watanabe, Nobuya Mori, and Kenji Taniguchi. "Impact of Self-Heating Effect on the Electrical Characteristics of Nanoscale Devices." Key Engineering Materials 470 (February 2011): 14–19. http://dx.doi.org/10.4028/www.scientific.net/kem.470.14.
Abstract:
Hot phonon generation and its impact on the current conduction in a nanoscale Si-device are investigated using a Monte Carlo simulation technique. In the quasi-ballistic transport regime, electrons injected from the source lose their energies mainly by emitting optical phonons in the drain. Due to the slow group velocity of the optical phonons, the efficiency of the heat dissipation is so poor that a region with a nonequilibrium phonon distribution, i.e., a hot spot, is created. In this study, we have implemented the hot phonon effect in an ensemble Monte Carlo simulator for the electron transport, and carried out the steady state simulations. Although it is confirmed that the optical phonon temperature in the hot spot is larger than that of acoustic phonons by > 100 K, the electron current density is not significantly affected. The local heating would degrade the hot electron cooling efficiency and the parasitic resistance in the drain, but they have a minor impact on the quasi-ballistic electron transport from the source to the drain.
12
Singh, Anu, Hempal Singh, Vinod Ashokan, and B. D. Indu. "Electrons and Phonons in High Temperature Superconductors." Journal of Materials 2013 (February 14, 2013): 1–4. http://dx.doi.org/10.1155/2013/605929.
Abstract:
The defect-induced anharmonic phonon-electron problem in high-temperature superconductors has been investigated with the help of double time thermodynamic electron and phonon Green’s function theory using a comprehensive Hamiltonian which includes the contribution due to unperturbed electrons and phonons, anharmonic phonons, impurities, and interactions of electrons and phonons. This formulation enables one to resolve the problem of electronic heat transport and equilibrium phenomenon in high-temperature superconductors in an amicable way. The problem of electronic heat capacity and electron-phonon problem has been taken up with special reference to the anharmonicity, defect concentration electron-phonon coupling, and temperature dependence.
13
Wang, Zan, Lei Quan, and Yi Wu Ruan. "Simulation of Electron Transport in Silicon using Monte Carlo Method." Advanced Materials Research 284-286 (July 2011): 871–74. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.871.
Abstract:
A Monte Carlo method is employed to investigate the properties of electron transport with considerations of electron-phonon scattering including intervalley scattering and intravalley scattering. Under different electric fields, the coupling relations between electrons and phonons are studied, and the behaviors of absorbing and releasing phonons from electrons are also analyzed. The results show the scattering events of absorbing phonons from electrons decrease with the increasing simulation time. At the same temperature, the mean free path of electron increases initially and then decreases with the increasing electric field intensity, and finally approaches an asymptotic value.
14
Khatami, Mohammad Mahdi, Gautam Gaddemane, Maarten L. Van de Put, Massimo V. Fischetti, Mohammad Kazem Moravvej-Farshi, Mahdi Pourfath, and William G. Vandenberghe. "Electronic Transport Properties of Silicane Determined from First Principles." Materials 12, no. 18 (September 11, 2019): 2935. http://dx.doi.org/10.3390/ma12182935.
Abstract:
Silicane, a hydrogenated monolayer of hexagonal silicon, is a candidate material for future complementary metal-oxide-semiconductor technology. We determined the phonon-limited mobility and the velocity-field characteristics for electrons and holes in silicane from first principles, relying on density functional theory. Transport calculations were performed using a full-band Monte Carlo scheme. Scattering rates were determined from interpolated electron–phonon matrix elements determined from density functional perturbation theory. We found that the main source of scattering for electrons and holes was the ZA phonons. Different cut-off wavelengths ranging from 0.58 nm to 16 nm were used to study the possible suppression of the out-of-plane acoustic (ZA) phonons. The low-field mobility of electrons (holes) was obtained as 5 (10) cm2/(Vs) with a long wavelength ZA phonon cut-off of 16 nm. We showed that higher electron (hole) mobilities of 24 (101) cm2/(Vs) can be achieved with a cut-off wavelength of 4 nm, while completely suppressing ZA phonons results in an even higher electron (hole) mobility of 53 (109) cm2/(Vs). Velocity-field characteristics showed velocity saturation at 3 × 105 V/cm, and negative differential mobility was observed at larger fields. The silicane mobility was competitive with other two-dimensional materials, such as transition-metal dichalcogenides or phosphorene, predicted using similar full-band Monte Carlo calculations. Therefore, silicon in its most extremely scaled form remains a competitive material for future nanoscale transistor technology, provided scattering with out-of-plane acoustic phonons could be suppressed.
15
Park, Jungkyu. "Thermal Transport Study in a Strained Carbon Nanotube and Graphene Junction Using Phonon Wavepacket Analysis." C 9, no. 1 (February 11, 2023): 21. http://dx.doi.org/10.3390/c9010021.
Abstract:
This study investigates single-mode phonon scattering from a junction structure consisting of a (6,6) single-walled carbon nanotube (SWCNT) and graphene, subject to mechanical deformation, using phonon wavepacket analysis. Results show that longitudinal acoustic (LA) and transverse acoustic (TA) phonons at low frequencies are transmitted more effectively through the SWCNT–graphene junction when the junction is deformed. As low-frequency phonons in LA and TA modes are major energy carriers, it is expected that thermal transport across the SWCNT–graphene junction will be more efficient when the junction is deformed. Interfacial thermal resistance across the SWCNT-graphene junction was calculated using reverse nonequilibrium molecular dynamics (RNEMD). The RNEMD results show that the interfacial thermal resistance decreases when the structure is elongated, deforming the junction between the SWCNT and graphene. However, there was no notable difference in the transmission of twisting (TW) and flexural (FO) phonons when the junction was deformed. The study also showed that the transmission of phonon energy through the SWCNT–graphene junction has a slight dependence on the group velocity of phonons, with phonons having higher group velocities transmitting the junction more effectively. The findings of this research will play a significant role in advancing the development of futuristic electronics by providing a tool for developing 3D carbon nanostructures with high thermal performance under mechanical deformation.
16
Luo, Tian-Lin, Ya-Fei Ding, Bao-Jie Wei, Jian-Ying Du, Xiang-Ying Shen, Gui-Mei Zhu, and Bao-Wen Li. "Phonon thermal conduction and thermal regulation in low-dimensional micro-nano scale systems: Non equilibrium statistical physics problems from chip heat dissipation." Acta Physica Sinica 72, no. 23 (2023): 234401. http://dx.doi.org/10.7498/aps.72.20231546.
Abstract:
“Heat death”, namely, overheating, which will deteriorate the function of chips and eventually burn the device and has become an obstacle in the roadmap of the semiconductor industry. Therefore, heat dissipation becomes a key issue in further developing semiconductor. Heat conduction in chips encompasses the intricate dynamics of phonon conduction within one-dimensional, two-dimensional materials, as well as the intricate phonon transport through interfaces. In this paper, the research progress of the complexities of phonon transport on a nanoscale in recent three years, especially the size dependent phonon heat transport and the relationship between anomalous heat conduction and anomalous diffusion are summarized. Further discussed in this paper is the fundamental question within non-equilibrium statistical physics, particularly the necessary and sufficient condition for a given Hamiltonian whose macroscopic transport behavior obeys Fourier’s law. On the other hand, the methods of engineering the thermal conduction, encompassing isotope doping, nanophononic crystals, interfacial phenomena, and phonon condensation are also introduced. In order to comprehensively understand the phonon thermal conduction, a succinct overview of phonon heat transport phenomena, spanning from thermal quantization and the phonon Hall effect to the chiral phonons and their intricate interactions with other carriers is presented. Finally, the challenges and opportunities, and the potential application of phonons in quantum information are also discussed.
17
Zhao, Yongsheng, Fengyun Yan, Xue Liu, Hongfeng Ma, Zhenyu Zhang, and Aisheng Jiao. "Thermal Transport Properties of Diamond Phonons by Electric Field." Nanomaterials 12, no. 19 (September 28, 2022): 3399. http://dx.doi.org/10.3390/nano12193399.
Abstract:
For the preparation of diamond heat sinks with ultra-high thermal conductivity by Chemical Vapor Deposition (CVD) technology, the influence of diamond growth direction and electric field on thermal conductivity is worth exploring. In this work, the phonon and thermal transport properties of diamond in three crystal orientation groups (<100>, <110>, and <111>) were investigated using first-principles calculations by electric field. The results show that the response of the diamond in the three-crystal orientation groups presented an obvious anisotropy under positive and negative electric fields. The electric field can break the symmetry of the diamond lattice, causing the electron density around the C atoms to be segregated with the direction of the electric field. Then the phonon spectrum and the thermodynamic properties of diamond were changed. At the same time, due to the coupling relationship between electrons and phonons, the electric field can affect the phonon group velocity, phonon mean free path, phonon–phonon interaction strength and phonon lifetime of the diamond. In the crystal orientation [111], when the electric field strength is ±0.004 a.u., the thermal conductivity is 2654 and 1283 , respectively. The main reason for the change in the thermal conductivity of the diamond lattice caused by the electric field is that the electric field has an acceleration effect on the extranuclear electrons of the C atoms in the diamond. Due to the coupling relationship between the electrons and the phonons, the thermodynamic and phonon properties of the diamond change.
18
Mazumder, Sandip, and Arunava Majumdar. "Monte Carlo Study of Phonon Transport in Solid Thin Films Including Dispersion and Polarization." Journal of Heat Transfer 123, no. 4 (January 20, 2001): 749–59. http://dx.doi.org/10.1115/1.1377018.
Abstract:
The Boltzmann Transport Equation (BTE) for phonons best describes the heat flow in solid nonmetallic thin films. The BTE, in its most general form, however, is difficult to solve analytically or even numerically using deterministic approaches. Past research has enabled its solution by neglecting important effects such as dispersion and interactions between the longitudinal and transverse polarizations of phonon propagation. In this article, a comprehensive Monte Carlo solution technique of the BTE is presented. The method accounts for dual polarizations of phonon propagation, and non-linear dispersion relationships. Scattering by various mechanisms is treated individually. Transition between the two polarization branches, and creation and destruction of phonons due to scattering is taken into account. The code has been verified and evaluated by close examination of its ability or failure to capture various regimes of phonon transport ranging from diffusive to the ballistic limit. Validation results show close agreement with experimental data for silicon thin films with and without doping. Simulation results show that above 100 K, transverse acoustic phonons are the primary carriers of energy in silicon.
19
Solanki, Reena, and Seema Agrawal. "Thermoelectric Properties of Zn Nanowires: Phonon Scattering Effect." Research Journal of Chemistry and Environment 26, no. 5 (April 25, 2022): 114–18. http://dx.doi.org/10.25303/2605rjce114118.
Abstract:
The temperature-dependent thermoelectric power (S) of Zn nanostructures is numerically estimated using a theoretical model. The electron diffusive and phonon drag contributions to thermoelectric power are calculated within the relaxation time approximation. The phonon drag thermopower is an artifact of various operating scattering mechanisms. The anomalous behavior of (S) is successfully estimated in accordance with interaction of heat carrying phonons with impurity, grain boundaries, electrons and phonons. The scattering and transport cross sections are function of phonon frequency in the present model and produce similar results.
20
Ali, Haider, and Bekir Sami Yilbas. "Thermal transport across a pair of thin silicon films with the presence of minute vacuum gap: effect of film thickness on thermal characteristics." Canadian Journal of Physics 94, no. 9 (September 2016): 933–44. http://dx.doi.org/10.1139/cjp-2016-0241.
Abstract:
Energy transport across a pair of thin silicon films with the vacuum gap at the films interface is studied. The Boltzmann transport equation is incorporated in the analysis and the solution for the transient frequency-dependent phonon distribution across the films pair is presented. To assess the phonon characteristics, equivalent equilibrium temperature is introduced, which resembles the average energy of all phonons around a local point when they redistribute adiabatically to an equilibrium state. Because the gap size is comparable to the mean free path of silicon, a near-field radiation heat transfer is incorporated across the film edges at the interface. The frequency cutoff method is used at the interface of the films and the phonons jump across the gap resembling the ballistic phonon contribution to the energy transport is accommodated. The thermal conductivity data predicted are validated with the data obtained from the previous study. The effect of near-field radiation heat transfer on temperature increase at the edges of the film, across the gap interface, is not considerable as compared to that corresponding to phonons transmitted across the gap. Increasing the first film thickness increases temperature difference across the gap, which is more pronounced for large gap sizes.
21
Gopalan, Sanjay, Gautam Gaddemane, Maarten L. Van de Put, and Massimo V. Fischetti. "Monte Carlo Study of Electronic Transport in Monolayer InSe." Materials 12, no. 24 (December 14, 2019): 4210. http://dx.doi.org/10.3390/ma12244210.
Abstract:
The absence of a band gap in graphene makes it of minor interest for field-effect transistors. Layered metal chalcogenides have shown great potential in device applications thanks to their wide bandgap and high carrier mobility. Interestingly, in the ever-growing library of two-dimensional (2D) materials, monolayer InSe appears as one of the new promising candidates, although still in the initial stage of theoretical studies. Here, we present a theoretical study of this material using density functional theory (DFT) to determine the electronic band structure as well as the phonon spectrum and electron-phonon matrix elements. The electron-phonon scattering rates are obtained using Fermi’s Golden Rule and are used in a full-band Monte Carlo computer program to solve the Boltzmann transport equation (BTE) to evaluate the intrinsic low-field mobility and velocity-field characteristic. The electron-phonon matrix elements, accounting for both long- and short-range interactions, are considered to study the contributions of different scattering mechanisms. Since monolayer InSe is a polar piezoelectric material, scattering with optical phonons is dominated by the long-range interaction with longitudinal optical (LO) phonons while scattering with acoustic phonons is dominated by piezoelectric scattering with the longitudinal (LA) branch at room temperature (T = 300 K) due to a lack of a center of inversion symmetry in monolayer InSe. The low-field electron mobility, calculated considering all electron-phonon interactions, is found to be 110 cm2V−1s−1, whereas values of 188 cm2V−1s−1 and 365 cm2V−1s−1 are obtained considering the long-range and short-range interactions separately. Therefore, the calculated electron mobility of monolayer InSe seems to be competitive with other previously studied 2D materials and the piezoelectric properties of monolayer InSe make it a suitable material for a wide range of applications in next generation nanoelectronics.
22
Sasihithlu, K., J. B. Pendry, and R. V. Craster. "Van der Waals Force Assisted Heat Transfer." Zeitschrift für Naturforschung A 72, no. 2 (February 1, 2017): 181–88. http://dx.doi.org/10.1515/zna-2016-0361.
Abstract:
AbstractPhonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons), it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed [J. B. Pendry, K. Sasihithlu, and R. V. Craster, Phys. Rev. B 94, 075414 (2016)] by which phonons can transport heat across a vacuum gap – through the Van der Waals interaction between two bodies with gap less than the wavelength of light. Such heat transfer mechanisms are highly relevant for heating (and cooling) of nanostructures; the heating of the flying heads in magnetic storage disks is a case in point. Here, the theoretical derivation for modelling phonon transmission is revisited and extended to the case of two bodies made of different materials separated by a vacuum gap. Magnitudes of phonon transmission, and hence the heat transfer, for commonly used materials in the micro- and nano-electromechanical industry are calculated and compared with the calculation of conduction heat transfer through air for small gaps as well as the heat transfer calculation due to photon exchange.
23
LI, SHU-JUAN, GUI-FANG HUANG, YUAN CHEN, WEI-QING HUANG, WANGYU HU, LING-LING WANG, and ANLIAN PAN. "BALLISTIC PHONON TRANSPORT THROUGH GAUSSIAN ACOUSTIC NANOCAVITIES." Modern Physics Letters B 25, no. 19 (July 30, 2011): 1631–42. http://dx.doi.org/10.1142/s0217984911026954.
Abstract:
We investigate ballistic phonon transport through Gaussian acoustic nanocavities in a semiconductor nanowire at low temperatures. When the transverse widths of acoustic nanocavities takes a Gaussian function, it is found that wide band gap and resonant peaks appear in transmission spectra. The phonon-cavity confined modes exist as the number of the nanocavities is large. The phonon transmission and thermal conductance strongly depend on the number and length of nanocavities. The results suggest that the Gaussian acoustic nanocavities may be useful for controlling thermal conductance artificially and the design of phonon devices to manipulate ballistic phonons in nanophononics.
24
Singh, Dhanishtha, Roman Anufriev, and Masahiro Nomura. "Parabolic mirrors collimating and focusing fluxes of thermal phonons." Applied Physics Letters 122, no. 9 (February 27, 2023): 092203. http://dx.doi.org/10.1063/5.0137221.
Abstract:
Manipulating heat fluxes at the nanoscale has become increasingly important in modern microelectronics. However, many methods of heat manipulations rely on complex nanofabrication. Here, we propose simple designs for collimation and focusing of thermal phonons based on parabolic mirrors that require no nanofabrication. We perform Monte Carlo simulations of a ballistic phonon transport in silicon membranes with parabolic boundaries. Our simulations demonstrate that parabolic surfaces can act as parabolic mirrors for phonons, thus collimating or focusing phonon fluxes in semiconductors. Such parabolic mirrors can create a directional flux of thermal phonons emitted from a nanoscale hot spot or focus a collimated phonon flux into a hot spot. These devices open new possibilities in the thermal management of low-temperature systems, such as quantum circuits or cryogenic particle detectors.
25
Jacoboni, C., A. Abramo, P. Bordone, R. Brunetti, and M. Pascoli. "Application of the Wigner-Function Formulation to Mesoscopic Systems in Presence of Electron-Phonon Interaction." VLSI Design 8, no. 1-4 (January 1, 1998): 185–90. http://dx.doi.org/10.1155/1998/71098.
Abstract:
A theoretical and computational analysis of the quantum dynamics of charge carriers in presence of electron-phonon interaction based on the Wigner function is here applied to the study of transport in mesoscopic systems. Numerical applications are shown for a) a wave packet scattering with phonons while crossing a potential profile and b) electrons scattering with phonons in a finite device with open boundary conditions.
26
Sato, M., Y. Takahara, M. Matsumoto, N. Kajinami, M. Hanaoka, and M. Iwakawa. "Thermal control of thin films with nano structure." Journal of Physics: Conference Series 2766, no. 1 (May 1, 2024): 012206. http://dx.doi.org/10.1088/1742-6596/2766/1/012206.
Abstract:
Abstract Thermoelectric energy conversions have been attracting much attention, which directly generate electric energy from thermal one by utilizing the Seebeck effect. Among various efforts to improve the conversion efficiency, control of phonon propagation with nano-scale structures has been popular, which utilize phonon scatterings on structural interfaces. The concept is based on the difference of mean free path (MFP) between phonons and electrons (charge carriers). In typical cases with silicon-base devices, MFP of phonons is in an order of 100 nm while that of electrons is 1-10 nm. Thus structures of 10-100 nm size are expected to be effective for suppressing the phonon heat transfer without much reducing the electric transport, leading to conversion efficiency improvement. We have developed a numerical scheme to investigate phonon transport based on the Boltzmann transport equation (BTE) for time development of the phonon distribution function. To treat various shapes of nano-scale structures, we have newly introduced a VOF (volume of fluid) like scheme. In the presentation, we will show results of several test systems of nano-structured Si thin films, with evaluation of effective electric conductivity, to discuss how much nano-scale structures improve the conversion efficiency.
27
DEBALD, STEFAN, TOBIAS BRANDES, and BERNHARD KRAMER. "NONLINEAR ELECTRON TRANSPORT THROUGH DOUBLE QUANTUM DOTS COUPLED TO CONFINED PHONONS." International Journal of Modern Physics B 17, no. 28 (November 10, 2003): 5471–75. http://dx.doi.org/10.1142/s0217979203020594.
Abstract:
The non-linear electron current through a double quantum dot embedded in a free standing quantum well is investigated. In such a model for a nano-size phonon cavity, the transport at low temperatures is mediated by the spontaneous emission of acoustic phonons. Phonon quantum size effects can be detected as steps in the current. Moreover, for our model we find van-Hove singularities in the phonon density of states that give rise to a strong, tuneable increase of phonon emission into characteristic modes. The emission characteristic, depending on the position of the dots in the cavity, is also considered.
28
Ren, Weijun, Jie Chen, and Gang Zhang. "Phonon physics in twisted two-dimensional materials." Applied Physics Letters 121, no. 14 (October 3, 2022): 140501. http://dx.doi.org/10.1063/5.0106676.
Abstract:
As one of the most effective manipulation means to control the physical properties of two-dimensional van der Waals stacking materials, the twisted angle periodically regulates the interlayer interaction potential by generating moiré patterns. The decrease in Brillouin zone size and the change of high symmetry direction caused by the interlayer twisted angle lead to the emergence of the hybrid folded phonons—moiré phonons, which have noticeable impacts on phonon properties. This paper reviews the recent developments and discoveries on phonon properties in twisted two-dimensional stacking homogeneous and heterogeneous systems and focuses on the impacts of the interlayer twisted angle on phonon dispersion, such as interlayer coupling phonon modes and moiré phonons. Meanwhile, we introduced the recent research on the influence of the interlayer twisted angle on phonon transport behavior along the in-plane and out-of-plane directions. In addition, the theoretical and experimental open questions and challenges faced in the phonon characteristics of twisted two-dimensional materials are discussed, and some possible solutions are put forward.
29
Vasileiadis, Thomas, Juan Sebastian Reparaz, and Bartlomiej Graczykowski. "Phonon transport in the gigahertz to terahertz range: Confinement, topology, and second sound." Journal of Applied Physics 131, no. 18 (May 14, 2022): 180901. http://dx.doi.org/10.1063/5.0073508.
Abstract:
Transport of heat and hypersound with gigahertz (GHz) to terahertz (THz) phonons is crucial for heat management in electronics, mediating signal processing with microwave radiation, thermoelectrics, and various types of sensors based on nanomechanical resonators. Efficient control of heat and sound transport requires new materials, novel experimental techniques, and a detailed knowledge of the interaction of phonons with other elementary excitations. Wave-like heat transport, also known as second sound, has recently attracted renewed attention since it provides several opportunities for overcoming some of the limitations imposed by diffusive transport (Fourier’s regime). The frequency-domain detection of GHz-to-THz phonons can be carried out in a remote, non-destructive, and all-optical manner. The ongoing development of nanodevices and metamaterials made of low-dimensional nanostructures will require spatially resolved, time-resolved, and anisotropic measurements of phonon-related properties. These tasks can be accomplished with Brillouin light scattering (BLS) and various newly developed variants of this method, such as pumped-BLS. In the near future, pumped-BLS is expected to become useful for characterizing GHz topological nanophononics. Finally, second-sound phenomena can be observed with all-optical methods like frequency-domain thermoreflectance.
30
Khvesyuk, V. I., W. Qiao, and A. A. Barinov. "Kinetics of Phonon Interaction Taken into Account in Determining Thermal Conductivity of Silicon." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 3 (102) (June 2022): 57–68. http://dx.doi.org/10.18698/1812-3368-2022-3-57-68.
Abstract:
The thorough study of the heat carriers --- quasiparticles --- phonons interaction resulted in a pioneering method for calculating the thermal conductivity of nonmetallic solids. As the interactions of phonons are much more complicated than those of usual atoms and molecules, it is necessary to take into account the presence of two types of phonons with different properties; the decay of one phonon into two or the fusion of two phonons into one as a result of interaction; the presence of two types of interaction of phonons, one of which is elastic, the other is inelastic (moreover, the type of interaction results from solving the energy and quasi-momentum conservation equations). The existing methods for determining thermal conductivity, which typically involve solving the Boltzmann transport equation, use the iteration method, whose parameter is the average time between successive phonon interactions, and the calculation results provide little information on all types of interactions. In this research, we developed a method of direct Monte Carlo simulation of phonon diffusion with strict account for their interaction owing to the energy and quasi-momentum conservation laws. Calculations of the thermal conductivity coefficient for pure silicon in the temperature range of 100---300 K showed good agreement with the experiment and calculations of other authors, and also made it possible to consider the phonon kinetics in detail
31
CHOUDHARY, K. K., D. PRASAD, K. JAYAKUMAR, and DINESH VARSHNEY. "PHONON DRAG, CARRIER DIFFUSIVE THERMOELECTRIC POWER AND SEMICONDUCTING RESISTIVITY BEHAVIOR OF Zn NANOWIRES." International Journal of Nanoscience 09, no. 05 (October 2010): 453–59. http://dx.doi.org/10.1142/s0219581x10007022.
Abstract:
In this paper, we undertake a quantitative analysis of observed temperature-dependent thermoelectric power (S) of 4 nm Zn /Vycor composite nanowires by developing a model Hamiltonian that incorporates scattering of acoustic phonons with impurities, grain boundaries, charge carriers and phonons. Mott expression is used to determine the carrier diffusive thermoelectric power [Formula: see text]. The [Formula: see text] shows linear temperature dependence and the computed [Formula: see text] when subtracted from the experimental data is interpreted as phonon drag thermoelectric power [Formula: see text]. The model Hamiltonian within the relaxation time approximation sets the limitations of the scattering of acoustic phonons with impurities, grain boundaries, charge carriers and phonons for thermoelectric power in the nanowires. It is shown that for acoustic phonons the scattering and transport cross sections are proportional to fourth power of the phonon in the Rayleigh regime. The resultant thermoelectric powers is an artefact of various operating scattering mechanisms and are computed for the first time to our knowledge for Zn nanowires consistent with the experimentally reported behavior. The semiconducting nature of resistivity is discussed with small polaron conduction (SPC) model which consistently retraces the temperature-dependent resistivity behavior of Zn /Vycor composite.
32
Lan, Tian, and Zhaoyan Zhu. "Renormalized Phonon Microstructures at High Temperatures from First-Principles Calculations: Methodologies and Applications in Studying Strong Anharmonic Vibrations of Solids." Advances in Condensed Matter Physics 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/2714592.
Abstract:
While the vibrational thermodynamics of materials with small anharmonicity at low temperatures has been understood well based on the harmonic phonons approximation, at high temperatures, this understanding must accommodate how phonons interact with other phonons or with other excitations. To date the anharmonic lattice dynamics is poorly understood despite its great importance, and most studies still rely on the quasiharmonic approximations. We shall see that the phonon-phonon interactions give rise to interesting coupling problems and essentially modify the equilibrium and nonequilibrium properties of materials, for example, thermal expansion, thermodynamic stability, heat capacity, optical properties, thermal transport, and other nonlinear properties of materials. The review aims to introduce some recent developements of computational methodologies that are able to efficiently model the strong phonon anharmonicity based on quantum perturbation theory of many-body interactions and first-principles molecular dynamics simulations. The effective potential energy surface of renormalized phonons and structures of the phonon-phonon interaction channels can be derived from these interdependent methods, which provide both macroscopic and microscopic perspectives in analyzing the strong anharmonic phenomena while the traditional harmonic models fail dramatically. These models have been successfully performed in the studies on the temperature-dependent broadenings of Raman and neutron scattering spectra, high temperature phase stability, and negative thermal expansion of rutile and cuprite structures, for example.
33
Dong, Yuan. "Thermal rectification based on phonon hydrodynamics and thermomass theory." Communications in Applied and Industrial Mathematics 7, no. 2 (June 1, 2016): 26–38. http://dx.doi.org/10.1515/caim-2016-0004.
Abstract:
AbstractThe thermal diode is the fundamental device for phononics. There are various mechanisms for thermal rectification, e.g. different temperature dependent thermal conductivity of two ends, asymmetric interfacial resistance, and nonlocal behavior of phonon transport in asymmetric structures. The phonon hydrodynamics and thermomass theory treat the heat conduction in a fluidic viewpoint. The phonon gas flowing through the media is characterized by the balance equation of momentum, like the Navier-Stokes equation for fluid mechanics. Generalized heat conduction law thereby contains the spatial acceleration (convection) term and the viscous (Laplacian) term. The viscous term predicts the size dependent thermal conductivity. Rectification appears due to the MFP supersession of phonons. The convection term also predicts rectification because of the inertia effect, like a gas passing through a nozzle or diffuser.
34
Ali, Haider, and Bekir Sami Yilbas. "Microscale Thermal Energy Transfer Between Thin Films with Vacuum Gap at Interface." Journal of Non-Equilibrium Thermodynamics 44, no. 2 (April 26, 2019): 123–42. http://dx.doi.org/10.1515/jnet-2018-0092.
Abstract:
Abstract Transfer of phonons through a silicon–diamond thin film pair with a nano-size gap at the interface is examined. The thin film pair is thermally disturbed by introducing 301 K at the silicon film left edge while keeping the other edges of the thin films at a low temperature (300 K). The radiative phonon transport equation is solved numerically to quantify the phonon intensity distribution in the combined films. The frequency dependent formulation of phonon transport is incorporated in the transient analysis. The thermal boundary resistance is adopted at the interface in the formulations. The near-field radiative heat transfer is also adopted at the gap interface, as the vacuum gap size falls within the Casimir limit. The predictions of thermal conductivity are validated through the thermocouple data. It is observed that predictions of thermal conductivity are in agreement with the experimental data. The ballistic phonons play a major role in energy transfer through the gap; their contribution is more significant than that of the near-field radiative heat transfer. Enlarging the size of the gap reduces the influence of the ballistic phonons on the energy transfer in the films. Increasing the silicon film thickness alters the energy transfer through the gap; in this case, the equivalent equilibrium temperature difference is increased at the interface.
35
Jin, Jae Sik, and Joon Sik Lee. "Electron–Phonon Interaction Model and Prediction of Thermal Energy Transport in SOI Transistor." Journal of Nanoscience and Nanotechnology 7, no. 11 (November 1, 2007): 4094–100. http://dx.doi.org/10.1166/jnn.2007.010.
Abstract:
An electron–phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron–phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron–phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron–phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron–phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon–phonon scattering rates are lower than 4 × 1010 s−1.
36
Jin, Jae Sik, and Joon Sik Lee. "Electron–Phonon Interaction Model and Prediction of Thermal Energy Transport in SOI Transistor." Journal of Nanoscience and Nanotechnology 7, no. 11 (November 1, 2007): 4094–100. http://dx.doi.org/10.1166/jnn.2007.18084.
Abstract:
An electron–phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron–phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron–phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron–phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron–phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon–phonon scattering rates are lower than 4 × 1010 s−1.
37
Luo, Jiaming, Tong Lin, Junjie Zhang, Xiaotong Chen, Elizabeth R. Blackert, Rui Xu, Boris I. Yakobson, and Hanyu Zhu. "Large effective magnetic fields from chiral phonons in rare-earth halides." Science 382, no. 6671 (November 10, 2023): 698–702. http://dx.doi.org/10.1126/science.adi9601.
Abstract:
Time-reversal symmetry (TRS) is pivotal for materials’ optical, magnetic, topological, and transport properties. Chiral phonons, characterized by atoms rotating unidirectionally around their equilibrium positions, generate dynamic lattice structures that break TRS. Here, we report that coherent chiral phonons, driven by circularly polarized terahertz light pulses, polarize the paramagnetic spins in cerium fluoride in a manner similar to that of a quasi-static magnetic field on the order of 1 tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found that the transient magnetization is only excited by pulses resonant with phonons, proportional to the angular momentum of the phonons, and growing with magnetic susceptibility at cryogenic temperatures. The observation quantitatively agrees with our spin-phonon coupling model and may enable new routes to investigating ultrafast magnetism, energy-efficient spintronics, and nonequilibrium phases of matter with broken TRS.
38
Stefanou, Antonios-Dimitrios, and Xanthippi Zianni. "The Effect of Width-Mismatch of Modulated Nanowaveguides on the Thermoelectric Efficiency." Micromachines 14, no. 10 (October 7, 2023): 1912. http://dx.doi.org/10.3390/mi14101912.
Abstract:
Width-modulated nanowaveguides are promising for thermoelectric efficiency enhancement because electron and phonon transport properties can be geometrically tuned for improved performance. The shape of the modulation profile drastically affects the transport properties. Optimization of the width modulation for simultaneous maximum thermoelectric transport and minimum thermal transport is challenging because of the interconnected electron and phonon transport properties. We addressed this problem by analysing the effect of each characteristic dimension of a single rectangular modulation unit on electron and phonon transport. We identified distinct behaviours for electrons and phonons. We reveal that whereas phonon thermal conductance decreases with increasing width-mismatch, the electron thermoelectric power factor shows a non-monotonic dependence. It is pointed out that optimal width-mismatch that maximizes thermoelectric efficiency is mainly determined by electron transport and should be identified by maximizing the thermoelectric power. Our work points to a new strategy of optimizing geometry-modulated metamaterials for maximum thermoelectric efficiency.
39
Mao, Yudong, Shouyu Liu, Jiying Liu, Mingzhi Yu, Xinwei Li, Moon Keun Kim, and Kaimin Yang. "Phonon Transport Characteristics of Nano-Silicon Thin Films Irradiated by Ultrafast Laser under Dispersion Relation." Buildings 14, no. 1 (January 13, 2024): 210. http://dx.doi.org/10.3390/buildings14010210.
Abstract:
The gray model simplifies calculations by ignoring phonon polarization, but sacrifices a certain level of computational accuracy. In effect, the frequency and wavevector of phonons form complex polarization patterns, which means their propagation modes and vibrational directions have different influences. Therefore, based on the phonon dispersion relations in silicon, the lattice Boltzmann method is used to analyze the phonon transport characteristics in nano-silicon films under ultrafast laser excitation. The results show that the total energy density distribution obtained by superimposing acoustic and optical branches exhibits multiple wave-like behaviors. Among them, the acoustic branch has excellent transfer capability, dominating the rate at which the total energy density reaches a steady state distribution, while the optical branch has stronger heat capacity characteristics, with a greater impact on the peak value of the total energy density. When the heat transfer approaches a steady state, the longitudinal optical branch surprisingly contributes up to 52.73%. This indicates that the often-neglected optical phonons should also receive sufficient attention. Additionally, compared to the results of the gray model, it is found that the dispersion model is preferred when more attention is paid to the propagation characteristics during phonon transport.
40
Narumanchi, Sreekant V. J., Jayathi Y. Murthy, and Cristina H. Amon. "Submicron Heat Transport Model in Silicon Accounting for Phonon Dispersion and Polarization." Journal of Heat Transfer 126, no. 6 (December 1, 2004): 946–55. http://dx.doi.org/10.1115/1.1833367.
Abstract:
In recent years, the Boltzmann transport equation (BTE) has begun to be used for predicting thermal transport in dielectrics and semiconductors at the submicron scale. However, most published studies make a gray assumption and do not account for either dispersion or polarization. In this study, we propose a model based on the BTE, accounting for transverse acoustic and longitudinal acoustic phonons as well as optical phonons. This model incorporates realistic phonon dispersion curves for silicon. The interactions among the different phonon branches and different phonon frequencies are considered, and the proposed model satisfies energy conservation. Frequency-dependent relaxation times, obtained from perturbation theory, and accounting for phonon interaction rules, are used. In the present study, the BTE is numerically solved using a structured finite volume approach. For a problem involving a film with two boundaries at different temperatures, the numerical results match the analogous exact solutions from radiative transport literature for various acoustic thicknesses. For the same problem, the transient thermal response in the acoustically thick limit matches results from the solution to the parabolic Fourier diffusion equation. In the acoustically thick limit, the bulk experimental value of thermal conductivity of silicon at different temperatures is recovered from the model. Experimental in-plane thermal conductivity data for silicon thin films over a wide range of temperatures are also matched satisfactorily.
41
Tang, Xiao-Fang, Shuang-Xing Zhu, Hao Liu, Chen Zhang, Qi-Yi Wu, Zi-Teng Liu, Jiao-Jiao Song, et al. "Growth, characterization, and Raman spectra of the 1T phases of TiTe2, TiSe2, and TiS2." Chinese Physics B 31, no. 3 (March 1, 2022): 037103. http://dx.doi.org/10.1088/1674-1056/ac306a.
Abstract:
High-quality large 1T phase of TiX 2 (X = Te, Se, and S) single crystals have been grown by chemical vapor transport using iodine as a transport agent. The samples are characterized by compositional and structural analyses, and their properties are investigated by Raman spectroscopy. Several phonon modes have been observed, including the widely reported A 1g and Eg modes, the rarely reported Eu mode (∼183 cm−1 for TiTe2, and ∼185 cm−1 for TiS2), and even the unexpected K mode (∼85 cm−1) of TiTe2. Most phonons harden with the decrease of temperature, except that the K mode of TiTe2 and the Eu and “A 2u /Sh” modes of TiS2 soften with the decrease of temperature. In addition, we also found phonon changes in TiSe2 that may be related to charge density wave phase transition. Our results on TiX 2 phonons will help to understand their charge density wave and superconductivity.
42
Sharma, Vineet Kumar, Birender Singh, Anan Bari Sarkar, Mayanak K. Gupta, Ranjan Mittal, Amit Agarwal, Bahadur Singh, and V. Kanchana. "Topological phonons and electronic structure of Li2BaSi class of semimetals." Journal of Physics: Condensed Matter 34, no. 12 (January 6, 2022): 125502. http://dx.doi.org/10.1088/1361-648x/ac4441.
Abstract:
Abstract Extension of the topological concepts to the bosonic systems has led to the prediction of topological phonons in materials. Here we discuss the topological phonons and electronic structure of Li2BaX (X = Si, Ge, Sn, and Pb) materials using first-principles theoretical modelling. A careful analysis of the phonon spectrum of Li2BaX reveals an optical mode inversion with the formation of nodal line states in the Brillouin zone. Our electronic structure results reveal a double band inversion at the Γ point with the formation of inner nodal-chain states in the absence of spin–orbit coupling (SOC). Inclusion of the SOC opens a materials-dependent gap at the band crossing points and transitions the system into a trivial insulator state. We also discuss the lattice thermal conductivity and transport properties of Li2BaX materials. Our results show that coexisting phonon and electron nontrivial topology with robust transport properties would make Li2BaX materials appealing for device applications.
43
Volkov, Yuri Aleksandrovich, Mikhail Borisovich Markov, and Ilya Alekseyevich Tarakanov. "Statistical particle in cell for solving the phonon Boltzmann equation." Keldysh Institute Preprints, no. 96 (2022): 1–16. http://dx.doi.org/10.20948/prepr-2022-96.
Abstract:
The propagation of heat in a crystal is considered as a process of transport of phonons – quasi-particles with quasi-momentum and energy. The Boltzmann kinetic equation is constructed for the phonon’s distribution function in the phase space. The scattering of phonons is modeled in the approximation of the time of relaxation of their distribution to the equilibrium state. The numerical algorithm for solving the kinetic equation is based on the statistical method of particles, which combines the solution of the phonons motion equations with stochastic modeling of their creation and annihilation. The results of the numerical solution of the problems of temperature relaxation in a crystal during heating of its surface and energy release in the volume are considered.
44
Jin, Jae Sik, Bong Jae Lee, and Hyun Jin Lee. "Analysis of phonon transport in silicon nanowires including optical phonons." Journal of the Korean Physical Society 63, no. 5 (September 2013): 1007–13. http://dx.doi.org/10.3938/jkps.63.1007.
45
Sidorova, M., A. D. Semenov, H.-W. Hübers, S. Gyger, and S. Steinhauer. "Phonon heat capacity and self-heating normal domains in NbTiN nanostrips." Superconductor Science and Technology 35, no. 10 (August 30, 2022): 105005. http://dx.doi.org/10.1088/1361-6668/ac8454.
Abstract:
Abstract Self-heating normal domains in thin superconducting NbTiN nanostrips with the granular structure were characterized via steady-state hysteretic current–voltage characteristics measured at different substrate temperatures. The temperature dependence and the magnitude of the current, which sustains a domain in equilibrium at different voltages, can only be explained with a phonon heat capacity noticeably less than expected for 3D Debye phonons. This reduced heat capacity coincides with the value obtained earlier from magnetoconductance and photoresponse studies of the same films. The rate of heat flow from electrons at a temperature T e to phonons in the substrate at a temperature T B is proportional to ( T e p − T B p ) with the exponent p ≈ 3, which differs from the exponents for heat flows mediated by the electron–phonon interaction or by escaping of 3D Debye phonons via the film/substrate interface. We attribute both findings to the effect of grains on the phonon spectrum of thin NbTiN films. Our findings are significant for understanding the thermal transport in superconducting devices exploiting thin granular films.
46
Ding, Zhong‐Ke, Yu‐Jia Zeng, Wangping Liu, Li‐Ming Tang, and Ke‐Qiu Chen. "Topological Phonons and Thermoelectric Conversion in Crystalline Materials." Advanced Functional Materials, April 5, 2024. http://dx.doi.org/10.1002/adfm.202401684.
Abstract:
AbstractTopological phononics, a fascinating frontier in condensed matter physics, holds great promise for advancing energy‐related applications. Topologically nontrivial phonons typically possess gapless edge or surface states. These exotic states of lattice vibrations, characterized by their nontrivial topology, offer unique opportunities for manipulating and harnessing energy transport. The exploration of topological phonons opens new avenues in understanding and controlling thermal transport properties, with potential applications in fields such as thermoelectric materials, phononic devices, and waste heat recovery. Here, an overview of concepts such as Berry curvature and topological invariants, along with the applications of phonon tight‐binding method and nonequilibrium Green's function method in the field of topological phononics is provided. This review encompasses the latest research progress of various topological phonon states within crystalline materials, including topological optical phonons, topological acoustical phonons, and higher‐order topological phonons. Furthermore, the study delves into the prospective applications of topological phonons in the realm of thermoelectric conversion, focusing on aspects like size effects and symmetry engineering.
47
Cheng, Chao, and Shaoqing Wang. "Molecular dynamics study on the contribution of anisotropic phonon transmission to thermal conductivity of silicon." Journal of Physics: Condensed Matter, August 22, 2022. http://dx.doi.org/10.1088/1361-648x/ac8bc1.
Abstract:
Abstract The analysis of the contribution of anisotropic phonon transmission to thermal conductivity is helpful to focus on high-energy phonons in heat transport. We calculated a series of anharmonic phonon properties and heat transport properties of Si by Fourier projection method from atomic trajectories. Under this theoretical scheme, we have obtained very consistent results with the experimental data through very low computational cost, especially the anharmonic phonon properties at high temperature. We carefully analyze the contribution of different phonons to thermal conductivity and the anisotropic feature of phonon. It is found that the longitudinal acoustic phonons have the special thermal broadening near the point L at the boundary of the Brillouin zone. The optical phonons cannot be safely ignored in the study of heat transport, especially the longitudinal optical phonon that shows a large contribution to thermal conductivity at room temperature. The thermal conductivity contribution of different phonons varies with temperature. The anisotropic features of the contribution of different phonons to thermal conductivity are mainly reflected in the short-wavelength phonons. Our work explains the reason why other research works have different opinions on whether LA phonon is the main contributor of thermal conductivity. These investigations also provide insights for further understanding phonon heat transport and distribution of high-energy phonons.
48
Chen, Jiao, Guofu Chen, and Zhaoliang Wang. "Thermal transport and phonon localization in periodic h-GaN/h-AlN superlattices." Journal of Physics: Condensed Matter, October 18, 2023. http://dx.doi.org/10.1088/1361-648x/ad0470.
Abstract:
Abstract The widely observed non-diffusive phonon thermal transport phenomenon in nanostructures is largely attributed to classical size effects, which ignore the characteristic of phonon wave. In this context, the crossover transition process from incoherent to coherent phonon transport in two-dimensional heterogeneous periodic h-GaN/h-AlN superlattices is demonstrated using a non-equilibrium molecular dynamics approach, where the localization behavior of thermal phonons is particularly significant. The results show that the thermal transport of the superlattice structure is affected by a combination of structural parameters and temperature. The thermal conductivity (TC) of the superlattice decreases and then increases as the interface density increases. Phonon-interface scattering dominates the incoherent phonon transport, while local phonons modulate the transport in the coherent region. Thus, the competition between phonon wave and particle properties causes the transition from incoherent to coherent phonon transport. In addition, as the TC valley depth slows down with increasing system temperature, the scattering of medium and high frequency phonons is enhanced and the phonon lifetime decreases. Research on localized phonons in superlattices provides theoretical support for thermal transport regulation in basal low-dimensional materials.
49
Burin, Alexander L., Igor V. Parshin, and Igor V. Rubtsov. "Maximum propagation speed and Cherenkov effect in optical phonon transport through periodic molecular chains." Journal of Chemical Physics 159, no. 5 (August 2, 2023). http://dx.doi.org/10.1063/5.0158201.
Abstract:
Optical phonons serve as the fast and efficient carriers of energy across periodic polymers due to their delocalization, large group velocity because of covalent bonding, and large energy quantum compared to that for acoustic phonons as it was observed in a number of recent measurements in different oligomers. However, this transport is dramatically sensitive to anharmonic interactions, including the unavoidable interaction with acoustic phonons responsible for transport decoherence, suppressing ballistic transport at long distances. Here, we show that this decoherence is substantially suppressed if the group velocity of optical phonons is less than the sound velocity of acoustic phonons; otherwise, ballistic transport is substantially suppressed by a Cherenkov-like emission of acoustic phonons. This conclusion is justified considering energy and momentum conservation during phonon absorption or emission and supported by the numerical evaluation of the lifetimes of the optical phonons. It is also consistent with the recent experimental investigations of ballistic optical phonon transport in oligomers with the minor exception of relatively short oligophenylenes.
50
Li, Qinshu, Fang Liu, Song Hu, Houfu Song, Susu Yang, Hailing Jiang, Tao Wang, et al. "Inelastic phonon transport across atomically sharp metal/semiconductor interfaces." Nature Communications 13, no. 1 (August 20, 2022). http://dx.doi.org/10.1038/s41467-022-32600-w.
Abstract:
AbstractUnderstanding thermal transport across metal/semiconductor interfaces is crucial for the heat dissipation of electronics. The dominant heat carriers in non-metals, phonons, are thought to transport elastically across most interfaces, except for a few extreme cases where the two materials that formed the interface are highly dissimilar with a large difference in Debye temperature. In this work, we show that even for two materials with similar Debye temperatures (Al/Si, Al/GaN), a substantial portion of phonons will transport inelastically across their interfaces at high temperatures, significantly enhancing interface thermal conductance. Moreover, we find that interface sharpness strongly affects phonon transport process. For atomically sharp interfaces, phonons are allowed to transport inelastically and interface thermal conductance linearly increases at high temperatures. With a diffuse interface, inelastic phonon transport diminishes. Our results provide new insights on phonon transport across interfaces and open up opportunities for engineering interface thermal conductance specifically for materials of relevance to microelectronics.