Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session K61: Electrons, Phonons, Electron-Phonon Scattering and Phononics VFocus
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Sponsoring Units: DCOMP DFD Chair: Marcelo Jaime, Los Alamos Natl Lab Room: Room 418 |
Tuesday, March 7, 2023 3:00PM - 3:36PM |
K61.00001: Engineering thermal transport in low dimensional systems Invited Speaker: Ilaria Zardo The recently growing research field called “Nanophononics” deals with the investigation and control of vibrations in solids at the nanoscale. Phonon engineering leads to a controlled modification of phonon dispersion, phonon interactions, and transport [1,2]. However, engineering and probing phonons and phonon transport at the nanoscale is a non-trivial problem. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K61.00002: Electron hopping heat transport in molecules Galen Craven The realization of single-molecule thermal conductance measurements has driven the need for theoretical tools to describe conduction processes that occur over atomistic length scales. In macroscale systems, the principle that is typically used to understand thermal conductivity is Fourier's law. At molecular length scales, however, deviations from Fourier's law are common in part because microscale thermal transport properties typically depend on the complex interplay between multiple heat conduction mechanisms. Here, the thermal transport properties that arise from electron hopping across a thermal gradient in a molecular conduction junction are examined theoretically. We illustrate how transport in a model junction is affected by varying the electronic structure and length of the molecular bridge in the junction as well as the strength of the coupling between the bridge and its surrounding environment. We show that the system's thermal conductance commonly deviates from Fourier's law and that, in properly engineered systems, the magnitude of electron hopping thermal conductance is similar to what has been measured in single-molecule devices. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K61.00003: Effects of high-order anharmonicity on the thermal transport in AgX (X=Cl, Br, I) OUYANG NIUCHANG, Yue Chen Recent studies showed the suppression of third-order anharmonicity can lead to an important role of the four-phonon scattering process on the thermal transport of solids. Herein, we investigate the lattice dynamics and thermal transport in AgX (X=Cl, Br, I) using perturbation theory up to the fourth order and a unified theory of thermal transport including population and coherence contributions. We find that the temperature renormalization of third-order force constants is significant for calculating the lattice thermal conductivities of AgCl and AgBr. Our results also show that the lattice thermal conductivity of AgI is overestimated even including fourth-order anharmonicity. Further simulation based on a force-constant potential suggests an important role of the fifth- and sixth-order phonon scattering processes in the lattice thermal transport of AgI. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K61.00004: Effect of higher-order anharmonicity on the phonon lineshapes in weakly-bonded solids from first principles Navaneetha Krishnan Ravichandran Recently, it has been shown computationally that the inclusion of higher-order anharmonic phonon renormalization and higher-order four-phonon scattering is crucial to accurately represent the thermal conductivities of weakly-bonded solids like sodium chloride (NaCl) [1]. Here we show, using our recently-developed unified first-principles framework, that four-phonon scattering also critically affects the phonon lineshapes of NaCl, typically observed in inelastic neutron and Raman scattering experiments. To capture these higher-order effects accurately, our calculations include the lowest-order three-phonon and higher-order four-phonon scattering processes, and a many-body self-consistent anharmonic phonon renormalization step to address the ill-defined nature of phonon quasiparticles. By performing these calculations over a broad range of temperatures, we show that four-phonon processes significantly broaden the phonon lineshapes compared to their three-phonon counterparts - particularly at high temperatures, and their inclusion into the calculations is pivotal to explain the experimental data. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K61.00005: Persistence of transverse phonons across liquid-like transition in superionic conductor KAg3Se2 Chen Wang, Yue Chen A fundamental understanding of unusual atomic dynamics and collective modes in superionic conductors has been of great importance in improving renewable energy technologies such as thermoelectric energy conversion and electrolytes for rechargeable batteries. Herein, we have performed an in-depth study of the lattice dynamics evolution across the superionic transition of KAg3Se2 by analyzing the thermally driven density fluctuations. We show that the diffuson-like phonons induced by the strong anharmonicity of Ag sublattice dominate thermal transport below the superionic transition, resulting in ultralow lattice thermal conductivity in the normal ordered state. We find that the contributions of convection and conduction-convection interactions to lattice thermal conductivity increase significantly due to the liquid-like flow of Ag atoms. We further demonstrate that the dynamic disorder is too slow to completely suppress the propagating of long-wavelength transverse phonons in the superionic state of KAg3Se2, while the Ag-dominated short-wavelength transverse phonons near the Brillouin zone boundary break down. These results provide new physical insights into the complex atomic dynamics of superionic conductors. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K61.00006: First-principles phonon calculations using self-consistent extended Hubbard functional Wooil Yang, Seung-Hoon Jhi, Young-Woo Son The local Hubbard interactions functionals are efficient ways to reduce the self-interaction errors in the local and semilocal functionals. We obtain on-site and inter-site Hubbard interaction parameters self-consistently based on the Agapito-Curtarolo-Buongiorno Nardelli pseudohybrid functional method. Then, we examine the electronic, structural, and phonon properties of group IV semiconductors and transition-metal oxides by using the newly proposed extended Hubbard functionals. The covalent bonding character of group IV semiconductors becomes stiff by including the extended Hubbard functionals, resulting in the longer three-phonon lifetimes and higher thermal conductivities. Also, we emphasize that the inter-site Hubbard terms are decisive in reducing the over-localization and in enhancing the orbital hybridizations between atom pairs. It also simulates the electronic dielectric constants and the ionic bonding characters very well. We demonstrate that the phonon dispersions of transition-metal oxides such as MnO and NiO are in good agreement with experiments and ones based on dynamical mean field theory without serious computational cost. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K61.00007: Bloch oscillations, Landau-Zener transition and the evolution of topological phase in the bulk of classical pendula arrays Izhar Neder We analyze theoretically and experimentally the dynamics of a one-dimensional array of pendula that have a mild gradient in their self-frequency and where neighboring pendula are linearly coupled with a weak and alternating coupling strength. We show that the dynamics of this classical system map onto the quantum Su-Schrieffer-Heeger (SSH) model of electrons on a lattice in the presence of an electric field. As a result, an initial localized excitation evolves according to a Schr"{o}dinger-like equation and shows phenomena such as Bloch oscillations, Landau-Zener (LZ) transition, and coupling between the isospin and the spatial degrees of freedom. The mapping of the pendula system in the weak coupling limit to the SSH model quantitatively predicts these phenomena over a broad range of the parameter values. Consequently, we use Bloch oscillations in the adiabatic regime to directly measure the non-trivial topological phase winding of the band in two ways: by comparing the phase evolution in two systems with interchanged couplings, and by comparing the phase evolution of the two isospin components in a single system's wave evolution. |
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