Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session L44: Heat Transport in Condensed Systems IFocus
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Sponsoring Units: DCOMP Chair: Vasili Perebeinos, State Univ of NY - Buffalo Room: 704 |
Wednesday, March 4, 2020 8:00AM - 8:36AM |
L44.00001: Beyond Fourier’s law: viscous heat equations Invited Speaker: Andrea Cepellotti Heat hydrodynamics is undergoing a renewed wave of interest, after it has been theoretically proposed to take place in 2D materials and recent experimental observations in graphite. In particular, heat hydrodynamics emerges when the momentum carried by phonons is weakly dissipated, making it possible, for example, to observe second-sound, a wave-like propagation of heat. The macroscopic description of this regime, however, is still object of investigations, as the commonly used Fourier’s law isn’t capable of describing hydrodynamic transport. |
Wednesday, March 4, 2020 8:36AM - 8:48AM |
L44.00002: Quantum thermal transport in glasses: the role of anharmonicity Michele Simoncelli, Francesco Mauri, Nicola Marzari Thermal transport in glasses is often described by the harmonic theory introduced by Allen and Feldman [Phys. Rev. Lett., 62(6) (1989)], where heat is carried by couplings between vibrational modes and disorder limits the thermal conductivity. Hitherto, the effects of anharmonicity on heat conduction in glasses have been investigated using molecular simulations, combined with empirical quantum corrections to address discrepancies with experiments at low temperature. Recently, a unified theory of thermal transport in crystals and glasses has been formulated [Simoncelli, Marzari, and Mauri, Nat. Phys., 15 (2019)], allowing to account rigorously for quantum and anharmonic effects also in glassy or disordered systems. Here, we show that quantum effects and anharmonicity are crucial to explain the increasing non-saturating trend of the thermal conductivity with temperature observed in silica glass --- and not explained by the saturating Allen-Feldman harmonic theory. We analyze amorphous silica as a prototypical glass and provide recipes to perform first-principles quantum thermal conductivity calculations in glasses, which are accurate over a wide temperature range. |
Wednesday, March 4, 2020 8:48AM - 9:00AM |
L44.00003: Thermal transport modeling of nanoscale graphene devices using a Peierls-Boltzmann treatment Ali Kefayati, Philip Allen, Vasili Perebeinos In nonmagnetic insulators, phonons are the carriers of heat. If heat enters in a region and temperature is measured at a point within a phonon mean free paths of the heated region, ballistic propagation causes a nonlocal relation between local temperature and heat insertion. Our work focuses on the solution of the Peierls-Boltzmann equation (PBE) for nanoscale graphene devices. We use a realistic anharmonic scattering potential and examine different approximations such as the relaxation time approximation and the definition of local temperature. The results illustrate the expected local (diffusive) response for minimum phonon mean free path lambda_min<<L, and a diffusive to ballistic crossover as lamba_min increases toward the scale of the device size L. |
Wednesday, March 4, 2020 9:00AM - 9:36AM |
L44.00004: Heat transport in resonant condensed systems: Thermal conductivity reduction by coherent mechanisms Invited Speaker: Mahmoud I. Hussein The notion of a locally resonant metamaterial—widely applied to light and sound—has recently been introduced to heat, whereby the thermal conductivity is reduced primarily by intrinsic localized atomic vibrations (vibrons) rather than scattering mechanisms. The localized vibration modes manifest by the introduction of intrinsic nanoresonators within, or attached to, a host crystalline material, ideally a semiconductor. The phonon band structure under such conditions exhibit a myriad of horizontal bands representing each resonant degree of freedom. These bands hybridize with the underlying phonon modes carrying the heat in the host medium, which leads to significant reductions in the phonon group velocities and to mode localizations within the nanoresonators. Moderate reductions in the phonon lifetimes also occur. The nature of nanoscale thermal conduction under such conditions is fundamentally transformed due to these effects. A key requirement for the realization of phonon-vibron couplings and the subsequent effects mentioned above is the presence of a sufficient level of coherent wave behavior, which is only possible when there is a relatively wide distribution of the phonon mean free path. An example of a “nanophononic metamaterial” is a silicon membrane with nanopillars distributed on the surface. In this work, we provide predictions—by theory and simulations—of the thermal transport properties of this system. |
Wednesday, March 4, 2020 9:36AM - 9:48AM |
L44.00005: Minimizing Heat Transport by Ballistic Confinement in Phononic Metalattices Weinan Chen, Disha Talreja, Devin Goodling, Pratibha Mahale, Nabila Nova, Hiu Cheng, Jennifer Russell, Shih-Ying Yu, Nicolas Poilvert, Gerald D Mahan, Suzanne Mohney, Vincent Crespi, Thomas Mallouk, John Badding, Brian Foley, Venkatraman Gopalan, Ismaila Dabo We study the thermal conductivity of phononic metalattices, a class of newly synthesized nanostructures exhibiting long-range periodicity commensurate with the mean free paths of the phonons. In this work, we present a computational approach that is capable of computing the ballistic phonon mean free paths in periodic metamaterials by embedding an explicit model of phonon radiation into a continuum density of scatters, closing the gap between existing analytical models and numerical simulations. Our computational predictions supported by sensitive measurements indicate that the thermal conductivity minimum of metalattices can be as low as 0.15 W/m/K, which is among the smallest lattice conductivities reported for two- and three-dimensional silicon-based materials. This exceptional reduction in the heat conductivity establishes metalattices as a useful platform to achieve order-of-magnitude tunability in the thermal response of crystalline semiconductors. |
Wednesday, March 4, 2020 9:48AM - 10:00AM |
L44.00006: Thermal boundary conductance of beyond graphene two-dimensional materials Cameron Foss, Zlatan Aksamija An ongoing concern for 2D materials is their ability to thermally couple with an underlying substrate which acts as the primary pathway for heat removal in 2D devices. The thermal pathway from the 2D layer to substrate has been studied rigorously in graphene and various transition metal dichalcogenides. However, the literature still lacks a comprehensive analysis of thermal boundary conductance (TBC) for beyond-graphene materials. Previously [2D Mater. 6 (2019) 025019] we have shown that the TBC depends strongly on the overlap of available phonon modes in the long-wavelength regime and found selection criteria for choosing the best substrate for TBC. Here we use first-principles calculations and phonon interface transport modeling to calculate the TBC of beyond-graphene 2D materials, such as; silicene, germanene, BAs, InAs, and blue and black phosphorene, on amorphous and crystalline substrates. Our results show the TBC for these 2D materials on amorphous SiO2 (a-SiO2) falls between 20-50 MW.m-2.K-1. A trend emerges that 2D materials with lower ZA branch frequencies have higher TBCs when placed on a-SiO2. Our results provide selection criteria for 2D materials that improve interfacial heat transport in 2D devices with amorphous and crystalline substrates. |
Wednesday, March 4, 2020 10:00AM - 10:12AM |
L44.00007: Spatially-Resolved Phonon Hydrodynamic Flow from First Principles Georgios Varnavides, Adam Jermyn, Polina Anikeeva, Prineha Narang Material hydrodynamic regimes are characterized by numerous scattering events, each of which conserves quasi-momentum and thus doesn’t oppose the flow of carriers. Recent observations of non-resistive carrier transport in two-dimensional materials suggest that hydrodynamic flow can occur over a wide range of temperatures1. In thermal transport, hydrodynamic flow manifests itself in two separate phenomena: the wavelike propagation of heat, termed second sound, and parabolic heat profiles, reminiscent of classical incompressible fluid pipe flow. |
Wednesday, March 4, 2020 10:12AM - 10:24AM |
L44.00008: Microscopic thermal transport mechanisms in Tl3VSe4: lattice phonons or localized oscillators? Yi Xia, Koushik Pal, Jiangang He, Vidvuds Ozolins, Christopher Mark Wolverton Recently, crystalline Tl3VSe4 was experimentally reported to exhibit an ultralow lattice thermal conductivity (κl) of 0.3±0.05 W/mK at 300 K [Science 360, 1455 (2018)]. Understanding of the underlying thermal transport mechanism has been deemed nontrivial, which requires a complex scenario that involves two channels: lattice phonons and localized oscillators. However, the observed Raman spectra, specific heat, and temperature dependence of κl only reveal features characteristic of phonons in an ordered crystalline compound. To resolve this conundrum, we investigate the heat transfer in Tl3VSe4 by combining a first-principles density-functional theory based framework of anharmonic lattice dynamics with the Peierls-Boltzmann transport equation for phonons. Specifically, we include contributions of the three- and four-phonon scattering processes to the phonon lifetimes as well as the temperature-dependent anharmonic renormalization of phonon energies. We reveal the dominant thermal transport mechanism by explicitly evaluating both diagonal (particle-like propagation) and off-diagonal (wave-like tunneling) terms of the heat current operator. |
Wednesday, March 4, 2020 10:24AM - 10:36AM |
L44.00009: Violation of the Wiedemann-Franz law in graphene: plasmon contribution to the heat conductivity Lars Fritz It is well established that close to the Dirac point in graphene the Wiedemann-Franz law is violated. Using a microscopic Boltzmann approach we first show that a theory of electrons and holes cannot quantitatively account for the heat conductivity observed in experiment. We argue that the missing heat conductivity is due to plasmons which make a sizeable contribution in the vicinity of the Dirac point. |
Wednesday, March 4, 2020 10:36AM - 10:48AM |
L44.00010: Influence of Adsorbed Liquid Monolayer Ordering on the Kapitza Resistance at Solid/Liquid Interfaces Hiroki Kaifu, Sandra Troian Applications ranging from small scale avionics control to AI computing platforms are ever more reliant on high density integrated chips prone to thermal runaway. Thermal extraction is now the limiting factor in information processing and so conventional air cooling is being displaced by microscale liquid cooling systems, which are more efficient due to the higher heat capacity of liquids. In this work, we use non-equilibrium MD simulations to examine thermal transport across solid/liquid (S/L) interfaces in quiescent fluids, as quantified by the Kapitza resistance. While previous studies have focused on interfacial behavior mediated by liquid density stratification, wettability and solid crystalline symmetry, we instead examine the influence of in-plane ordering within the first few liquid monolayers adsorbed at the solid surface. The characteristics of these proximal layers are tuned by varying the depth and repulsive distance characterizing the intermolecular potential. Our results, some intuitive and some not, yield general correlations between the Kapitza jump and measures of interfacial commensurability influenced by the structure and collective response of such monolayers. |
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