Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Z53: Invited Session: Thermal Transport: Modelling and Ab Initio Calculations |
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Sponsoring Units: DCOMP Chair: Matthias Scheffler, Fritz-Haber, Berlin, Germany Room: Grand Ballroom C3 |
Friday, March 6, 2015 11:15AM - 11:51AM |
Z53.00001: Interfacial Heat Conduction in Modern Semiconductor Nanostructures Invited Speaker: Kenneth Goodson Heat conduction through interfaces in electronic nanostructures grows more important with the dimensional scaling trends throughout the semiconductor industry. The complexity of interfacial transport has increased owing to frequent examples of severe lattice mismatch and strain, boundaries with nanoscale non-planar features and, in some cases, the critical role of electron-phonon interactions. This talk will describe measurements and modeling of phonon heat conduction through interfaces in some of the latest semiconductor nanotechnologies and feature a range of material combinations. Examples include GaN-diamond and silicon-diamond composites, chalcogenide-metal multilayers, metal-semiconductor nanolayer stacks, and nonplanar interfaces in modern nanotransistors and interconnect structures. Applications range from conventional CMOS electronics and phase change memory to quantum cascade lasers and RF amplifiers for satellites. [Preview Abstract] |
Friday, March 6, 2015 11:51AM - 12:27PM |
Z53.00002: Phonon hydrodynamics in two-dimensional materials Invited Speaker: Nicola Marzari The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific and technological applications of novel layered materials. Here, we use third order density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene and related materials (boron nitride, functionalized derivatives, transition-metal dichalcogenides...). Very good agreement is obtained with experimental data, where available, together with a microscopic understanding of the collective character of heat-carrying excitations, and the unusual length scales involved. Last, and at variance with typical three-dimensional solids, normal processes dominate over Umklapp scattering well above cryogenic conditions, extending to room temperature and more. As a result, novel hydrodynamics regimes, hitherto typically confined to ultra-low temperatures, become readily apparent. [Preview Abstract] |
Friday, March 6, 2015 12:27PM - 1:03PM |
Z53.00003: Accurate Thermal Conductivities from First Principles Invited Speaker: Christian Carbogno In spite of significant research efforts, a first-principles determination of the thermal conductivity at high temperatures has remained elusive. On the one hand, Boltzmann transport techniques\footnote{D. A. Broido {\em et al.}, {\em Appl. Phys. Lett.} {\bf 91}, 231922 (2007).} that include anharmonic effects in the nuclear dynamics only perturbatively become inaccurate or inapplicable under such conditions. On the other hand, non-equilibrium molecular dynamics (MD) methods suffer from enormous finite-size artifacts in the computationally feasible supercells, which prevent an accurate extrapolation to the bulk limit of the thermal conductivity~\footnote{ P. K. Schelling, S. R. Phillpot, and P. Keblinski, {\em Phys. Rev. B} {\bf 65}, 144306 (2002).}. In this work, we overcome this limitation by performing {\it ab initio}~MD simulations in thermodynamic equilibrium that account for all orders of anharmonicity. The thermal conductivity is then assessed from the auto-correlation function of the heat flux using the Green-Kubo formalism\footnote{R. Kubo, M. Yokota, S. Nakajima, {\em J. Phys. Soc. Jpn.} {\bf 12}, 1203 (1957).}. Foremost, we discuss the fundamental theory underlying a first-principles definition of the heat flux using the virial theorem. We validate our approach and in particular the techniques developed to overcome finite time and size effects,~e.g.,~by inspecting silicon, the thermal conductivity of which is particularly challenging to converge\footnote{Y. He {\em et al.}, {\em Phys. Chem. Chem. Phys.} {\bf 14}, 16209 (2012).}. Furthermore, we use this framework to investigate the thermal conductivity of ZrO$_2$, which is known for its high degree of anharmonicity. Our calculations shed light on the heat resistance mechanism active in this material, which eventually allows us to discuss how the thermal conductivity can be controlled by doping and co-doping\footnote{C. Carbogno {\em et al.}, {\em Phys. Rev. B} {\bf 90}, 144109 (2014).}. \newline This work has been performed in collaboration with R. Ramprasad~(University of Connecticut), C.~G.~Levi and C.~G.~Van~de~Walle~(University of California Santa Barbara). [Preview Abstract] |
Friday, March 6, 2015 1:03PM - 1:39PM |
Z53.00004: Modeling and Ab initio Calculations of Thermal Transport in Si-Based Clathrates and Solar Perovskites Invited Speaker: Yuping He We present calculations of the thermal transport coefficients of Si-based clathrates [1,2] and solar perovskites [3], as obtained from ab initio calculations and models, where all input parameters derived from first principles. We elucidated the physical mechanisms responsible for the measured low thermal conductivity in Si-based clatherates [1] and predicted their electronic properties and mobilities, which were later confirmed experimentally [2]. We also predicted that by appropriately tuning the carrier concentration, the thermoelectric figure of merit of Sn and Pb based perovskites may reach values ranging between 1 and 2, which could possibly be further increased by optimizing the lattice thermal conductivity through engineering perovskite superlattices.\\[4pt] [1] Y. He and G. Galli, \textbf{\textit{Nano. Lett. }}14, 2920 (2014).\\[0pt] [2] Y. He, F. Sui, S. M. Kauzlarich and G. Galli, \textbf{\textit{Energy Environ. Sci.}}7, 2386 (2014).\\[0pt] [3] Y. He and G. Galli, \textbf{\textit{Chem. Mat. }}26, 5394 (2014). [Preview Abstract] |
Friday, March 6, 2015 1:39PM - 2:15PM |
Z53.00005: The Importance of Complex Electronic Structures in Thermoelectric Materials Invited Speaker: David Singh Thermoelectric performance as characterized by the figure of merit, ZT, is a counter-indicated property of matter, meaning that high ZT depends on a combination of transport properties that do not generally occur together. A particularly important conundrum in thermoelectrics is the requirements for simultaneously having high electrical conductivity and high thermopower. I will argue that the resolution of this conundrum is through complex band structures and discuss how these arise in various known and predicted high performance thermoelectric materials. [Preview Abstract] |
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