Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session F58: Electrons, Phonons, ElectronPhonon Scattering, and Phononics IIIFocus

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Sponsoring Units: DCOMP Chair: Samuel Poncé, UCLouvain Room: 205D 
Tuesday, March 5, 2024 8:00AM  8:12AM 
F58.00001: Effects of SpinOrbit Coupling and Thermal Lattice Expansion on the Phononlimited Resistivity of Pb from First Principles Michel Côté, Felix Antoine Goudreault, Feliciano Giustino, Samuel Poncé In this presentation, we will report the results of calculations on the phononlimited temperaturedependent electrical resistivity of bulk Pb. Recent developments in computational techniques allow us to make quantitative comparisons between ab initio results of resistivity and experimental data. We use the approach of Wannier interpolation implemented in the EPW code to perform these calculations. The resistivity is computed by iteratively solving the selfconsistent linearized Boltzmann Transport Equation. Comparisons are made with the SERTA formulation of the resistivity. We observe that the lattice thermal expansion must be included to better compare to experimental data. We find that including spinorbit coupling (SOC) affects the results considerably. A softening of the phonon modes at the X point of the Brillouin zone is accentuated with SOC and with the increase of the unit cell volume. That volume change is obtained using the harmonic approximation of the free energy. Here again, we show the effect of including the SOC on the results obtained. Furthermore, we show that the temperature effects on the electronic free energy are negligible compared to the phononfree energy. 
Tuesday, March 5, 2024 8:12AM  8:24AM 
F58.00002: AbInitio calculated Low field transport properties in Supercells and its application to Alloys ANIMESH DATTA, Ankit Sharma, Uttam Singisetti To investigate the transport properties in random alloys, it is important to capture the alloy disorder using supercells. In case of supercells, the selfimage interaction error between the impurities is reduced and translational symmetry is explicitly imposed over larger length scales which traditional methods like Virtual Crystal Approximation fails to capture. In this work, we have investigated the polar optical phonon (POP) limited transport properties from firstprinciples calculations using supercells without unfolding the phonon dispersion. First, the phonon properties of GaN supercells are calculated and verified by comparing with the primitive cell. To validate our methods of supercell based mobility calculations, the Boltzmann Transport Equation is solved using Rode’s method to compare the POP and IIP limited mobility in the 4 atom GaN primitive cell and 12,40,32 atom GaN supercell. For random Al_{x}Ga_{1x}N alloy systems, the phonon dispersion properties are calculated using Density Functional Perturbation Theory on a 40atom random Al_{x}Ga_{1x}N system. Solving the Boltzmann Transport Equation iteratively our calculations predict a room temperature mobility of 189 cm^{2}/Vs at x=0.25 and 149 cm^{2}/Vs at x=0.5 Al fractions at n=1e18cm^{3} electron concentration which show that along with alloy scattering, electronphonon scattering also plays an important role at room temperature. This technique opens the path for calculating phonon limited transport properties in random alloy systems. 
Tuesday, March 5, 2024 8:24AM  8:36AM 
F58.00003: Strain Engineering of GaN for Hole Mobility Optimization: A comprehensive approach JieCheng Chen, Joshua A Leveillee, Chris G Van de Walle, Feliciano Giustino Gallium nitride (GaN) is a versatile wideband gap semiconductor vital for applications in power electronics, radiofrequency devices, and rapid switching transistors. However, its pchannel devices face a challenge due to low hole mobility, obstructing its integration into nextgeneration technologies. Various strain states have been explored individually to enhance hole mobility, but a comprehensive assessment of their collective impact is lacking. In this study, we establish a linear tensor equation that correlates hole mobility and applied strain in GaN. Our approach leverages ab initio Boltzmann transport equations, accounting for electronphonon scattering and quasiparticle energy corrections to derive hole mobilities. We use this knowledge to identify a set of optimal strain conditions, maximizing GaN hole mobility. Moreover, our methodology offers a general framework for firstprinciplesbased material property engineering through strain manipulation. 
Tuesday, March 5, 2024 8:36AM  9:12AM 
F58.00004: Firstprinciples transport including magnetic and spinorbit effects Invited Speaker: Matthieu J Verstraete Topology is the next frontier in materials science, opening possibilities for ultra low power devices, exquisite sensing capabilities, and synergies with quantum computing through the protection of state coherence. 
Tuesday, March 5, 2024 9:12AM  9:24AM 
F58.00005: High mobility 2D semiconductors: A computational search via the ab initio Boltzmann transport equation VietAnh Ha, Feliciano Giustino Higher integration density of transistor on chip requires the reduction of their channel lengths. However, shortchannel effect prevents transistor channel from being shrunk down to the scale of a few nanometers. Twodimensional materials offer a potential avenue to overcome this bottleneck. This materials family possesses danglingbondfree surfaces and can be used as transistor channels down to the subnanometer scale in their monolayer limit. However, most known 2D semiconductors exhibit low carrier mobility, as a result of their high density of states at band edges. In this work, we establish a highthroughput computing strategy to search for 2D semiconductors with high carrier mobility. Starting from available 2D materials database, we identify promising highmobility materials by evaluating the conductivity effective mass and by solving the ab initio Boltzmann transport equation. 
Tuesday, March 5, 2024 9:24AM  9:36AM 
F58.00006: Calculations of the nonlinear Hall effect with firstprinciples electronphonon collisions and Berry curvature Dhruv C Desai, JinJian Zhou, Marco Bernardi In certain topological materials, the application of an electric field results in a finite secondorder transverse Hall voltage, a phenomenon commonly known as the nonlinear Hall effect (NLHE). This recently discovered effect has gathered significant attention, primarily because it does not require the breaking of timereversal symmetry, unlike conventional Hall effects. Firstprinciples calculations have shown that intrinsic NLHE originates from the presence of a finite Berrycurvature dipole. However, accurately computing NLHE requires knowledge of both band topology and the electronic scattering mechanisms. In this talk, we combine firstprinciples Berry curvature and electronphonon scattering calculations to achieve a quantitative description of nonlinear Hall transport. We solve the Boltzmann equation including both Berry curvature and eph collisions, and apply our method to two prototypical systems – monolayer WSe_{2} and bilayer WTe_{2} – to demonstrate quantitative predictions of NLHE. 
Tuesday, March 5, 2024 9:36AM  9:48AM 
F58.00007: Coupled electronphonon transport and viscous thermoelectric equations Jennifer Coulter, Bo Peng, Michele Simoncelli Nondiffusive, hydrodynamiclike transport of charge or heat has been observed in several materials, and recent pioneering experiments have proposed the possible emergence of electronphonon bifluids. We introduce a firstprinciples computational framework to investigate these phenomena, showing that the macroscopic viscosity of electronsphonon bifluids is microscopically determined by composite 'relaxon' electronphonon excitations, and these excitations also describe electronphonon drag effects on standard thermoelectric transport coefficients. 
Tuesday, March 5, 2024 9:48AM  10:00AM 
F58.00008: Electronphonon Drag Effect on Thermal Conductivity in Twodimensional Materials Yujie Quan, Bolin Liao Electronphonon drag refers to the momentum exchange between nonequilibrium phonons and electrons, and its effect on electronic transport properties, including the Seebeck coefficient and mobility, has been widely studied. However, a systematic study of the impact of nonequilibrium electrons on thermal transport properties, i.e., how extra momentum flow from nonequilibrium electrons to phonons affects thermal conductivity, is still lacking. In this work, by solving the fully coupled electron and phonon Boltzmann transport equations with ab initio scattering parameters, we capture the nonnegligible effect of electron drag on thermal conductivity in twodimensional (2D) materials. We find that the electron drag effect can significantly increase thermal conductivity. Our study advances the understanding of the effect of nonequilibrium carriers on thermal transport and gives new insights into the nature of coupled electronphonon transport in 2D semiconductors. This work is based on research supported by the U.S. Air Force Office of Scientific Research under award number FA95502210468 and the National Science Foundation (NSF) under award number CBET1846927. Y.Q. also acknowledges the support from the Graduate Traineeship Program of the NSF Quantum Foundry via the QAMASEi program under award number DMR1906325 at the University of California, Santa Barbara (UCSB). 
Tuesday, March 5, 2024 10:00AM  10:12AM 
F58.00009: The Anharmonic LAttice DYNamics (ALADYN) suite of codes and thermal properties of materials from firstprinciples data Keivan Esfarjani, Yuan Liang, Safoura Nayebsadeghi, Bikash Timalsina, Ruoshi Sun We will present our work on the development of an anharmonic lattice dynamics model and its related codes. 
Tuesday, March 5, 2024 10:12AM  10:24AM 
F58.00010: Neural network assisted solution of the PeierlsBoltzmann Equation for phonon transport in semiconductors and insulators Navaneetha Krishnan Ravichandran Unusual heat flow phenomena, such as the hydrodynamic phonon transport, arise out of dissipationfree strong coupling among phonons in crystalline solids, and find applications in thermal cloaking and shielding of semiconductor devices. The PeierlsBoltzmann equation (PBE) governs the coupled dynamics, transport and equilibriation of phonons in these systems and its predictive first principles solution including three and fourphonon scattering processes, which could serve as a search tool for new materials, has been computationally very expensive, due to its high dimensionality and the need to resolve highly localized, temporally evolving interactions among phonons. To overcome this issue, we present a neural network scheme to solve the PBE, which enables rapid convergence of its steadystate solution and allows for computationally efficient high temporal resolution of localized interactions among phonons under transient transport conditions. We show that, even for materials with complex crystal geometries such as bulk MoS_{2}, graphite, wGaN and hBN, the neural network scheme significantly outperforms the conventional iterative solution of the PBE under both steadystate and transient conditions. Our findings highlight the computational advantages of this neural networkbased first principles solver for the PBE, which can significantly impact efficient computational search for new materials with exceptional thermal transport properties. 
Tuesday, March 5, 2024 10:24AM  10:36AM 
F58.00011: ABSTRACT WITHDRAWN

Tuesday, March 5, 2024 10:36AM  10:48AM 
F58.00012: Topological entropy controls thermal conductivity in disordered carbon polymorphs Kamil Iwanowski, Gabor Csanyi, Michele Simoncelli The structural and thermal properties of disordered carbon play a pivotal role in many diverse energy technologies: nanoporous carbon finds applications in batteries and supercapacitors; (defective) graphite serves as a moderator in nuclear reactors, where neutron irradiation causes structural changes and material's aging. Although experiments indicate a strong dependence of thermal conductivity on structural disorder, the fundamental relationship between atomistic structure and macroscopic conductivity remains unclear. Here we address this challenge, using the Wigner formulation of thermal transport, quantumaccurate machinelearning potentials, and realspace topological descriptors to shed light on how disorder in the atomic bond network affects thermal conductivity. We introduce a descriptor – topological entropy – which quantitatively captures the variability of local coordination environments, and we show that it correlates with thermal conductivity at a given density. Our research establishes disorder in the atomic bond topology as a fundamental degree of freedom to control and engineer thermal conductivity, calling for studies on how to practically control the local bonding topology. Finally, our findings also suggest the possibility to probe atomistic structural properties using thermalconductivity measurements. 
Tuesday, March 5, 2024 10:48AM  11:00AM 
F58.00013: Large Bandgap Renormalization in Cu_{2}Se: Liquidlike Behavior and ElectroPhonon Coupling Effects at Finite Temperatures Yuxuan Wang, Marios Zacharias, Xiao Zhang, Nick Pant, Pierre F P. Poudeu, Emmanouil Kioupakis ßCu_{2}Se is one of the most promising thermoelectric materials due to its abundance, low cost and toxicity yet high figure of merit. The reason lies in superionic Cu vibrations, which creates the phononliquid electroncrystal effect, inhibiting heat transport while maintaining high electrical conductivity. However, accurate characterization of the electronic structure remains a challenge due to the strong effects of polymorphism (local disorder), electronphonon coupling and phonon anharmonicity. DFT calculations on the high symmetry structure yields semimetallic behavior. In this work, we address the problem by treating the effects of symmetry breaking and hightemperature anharmonic vibrations utilizing the anharmonic special displacement method (ASDM). We determined the groundstate polymorphous structure following the recipe in ASDM and obtained a converged bandgap of 0.9 eV with a 4x4x4 supercell, which is in excellent agreement with experimental values. Further, we applied ASDM starting from the polymorphous structure and investigated the bandgap renormalization as a function of temperature, and found that increasing temperature reduces the bandgap by 0.06 eV. We layout a framework to elucidate how anharmonicity impacts the electronic properties and the thermoelectric performance of Cu_{2}Se. 
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