Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F55: Phonons and Thermal Transport at the Nanoscale IFocus Session Live
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Sponsoring Units: DMP Chair: Charles Harris, Sandia National Laboratories |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F55.00001: Identifying the bottlenecks for heat transport in metal-organic frameworks Sandro Wieser, Tomas Kamencek, Johannes P. Dürholt, Rochus Schmid, Natalia Bedoya-Martínez, Egbert Zojer Metal-organic frameworks (MOFs) represent a highly porous type of materials formed by metal nodes connected by organic linkers. Their modular nature enables an almost limitless pool of possible materials leading to a wide range of different applications like gas storage, gas separation or catalysis. Many of the processes occurring during these applications rely on the dissipation of heat. Therefore, it is crucial to understand the mechanism of heat transport processes in order to design MOFs tailored for specific applications. We employ non-equilibrium molecular dynamics simulations to determine the thermal conductivity for a selection of different MOFs and to spatially resolve barriers for heat transport. We identify the interface between node and linker, specifically the bond between the metal and oxygen atoms, as the major bottleneck for the flow of thermal energy. This bottleneck can be tuned by utilizing metals with different masses or by changing metal-linker bonding strengths. This strategy is demonstrated by investigating a series of modified isoreticular MOFs. Additional insight is gained by identifying the phonons most relevant for thermal transport and by analyzing their harmonic and anharmonic properties. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F55.00002: Boltzmann equation modeling of thin-film quasiballistic phonon transport from a cylindrical electron beam heat source Geoff Wehmeyer Electron beams with sub-10 nm diameters can be used as nanoscale heaters or thermometers, enabling new techniques to probe heat transfer in nanostructures. However, since the electron beam diameter is often smaller than the energy carrier mean free path, using Fourier’s law will underpredict the temperature rise due to electron-beam induced heating. Here, we solve the Boltzmann transport equation (BTE) under the relaxation time approximation to quantify electron-beam induced heating in thin dielectric samples. In both thin and thick samples, the full BTE solution is in agreement with a simple “resistors in series model” that sums the ballistic resistance and the typical Fourier conduction resistance (considering the thin-film size effect). For nanoscale thermometry applications, the temperature rise under typical imaging conditions is predicted to remain negligibly small (<1 K), even when considering the dominant ballistic thermal resistance. Therefore, this BTE modeling indicates that nanoscale thermometry methods are not expected to display electron beam heating artifacts, but that the ballistic resistance can be important in experiments using nanoscale heat sources. |
Tuesday, March 16, 2021 11:54AM - 12:30PM Live |
F55.00003: Nanoscale Thermal Transport in Hybrid Materials and across Interfaces Invited Speaker: Zhiting Tian Understanding nanoscale thermal transport processes is essential to design nanomaterials with desired thermal transport properties for thermal energy conversion and management. Despite the significant progress in thermal transport of inorganic crystals, thermal transport in more complicated materials and across material interfaces remains much less understood. In this talk, I will present my research group’s efforts to uncover nanoscale thermal transport mechanisms in hybrid organic-inorganic materials and across interfaces, using atomic modeling and experimental measurements. I will start with our study on phonon dynamics in hybrid perovskites using inelastic x-ray scattering. It provides useful insights into their ultralow thermal conductivity. I will then share our latest work on phonon Anderson localization in aperiodic superlattices, where we observe the direct evidence of phonon Anderson localization. Last but not least, I will present our recent development on anharmonic atomistic Green’s function, which allows us to capture the importance of inelastic scattering across the interfaces and observe quantum thermal rectification. |
Tuesday, March 16, 2021 12:30PM - 12:42PM Live |
F55.00004: Measuring Kapitza resistance versus interfacial properties at sub-Kelvin temperatures Nathaniel Smith, Zexi Lu, Anne Marie Chaka, Raymond A Bunker For many materials, thermal conductivity at ultra-low temperatures depends almost entirely on transport of phonons. Such phonon transport is generally well-understood in bulk materials but is much less well-explored at material interfaces. Interfaces are commonly the largest limiter of heat transport (especially between dissimilar materials) due to the large amount of scattering that occurs at the interface. At the ultra-low temperatures in a dilution refrigerator, dominant wavelengths can be much longer than interfacial features and it becomes increasingly difficult to understand how finite size effects affect interfacial phonon transport. An experimental apparatus has been constructed to measure heat flow across interfaces at mK temperatures. These experiments will be validated against both atomistic models and macroscopic finite element analysis models and will be used to quantify Kapitza resistance as a function of interfacial properties at sub-Kelvin temperatures. First results using the experimental apparatus will be presented. |
Tuesday, March 16, 2021 12:42PM - 12:54PM Live |
F55.00005: Thermal boundary conductance of buckled group IV,V, and III-V 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 in graphene and various transition metal dichalcogenides. However, the literature still lacks a comprehensive analysis of thermal boundary conductance (TBC) for beyond-graphene materials. 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, and blue and black phosphorene, on amorphous and crystalline substrates. Our results show that the TBC of uncoated 2D-3D systems can be substantially bottlenecked by weak internal repopulation of ZA phonons, which are the primary carriers of heat across the interface. However, we then demonstrate that encapsulation not only improves TBC through increasing the repopulation of ZA phonons in the 2D layer, but also weakens the temperature dependence at temperatures above the Debye temperature of the 2D material. Lastly, we employ our model to explore the TBC of vdW heterostructures formed with various 2D materials. Our results help provide a roadmap for improved 2D-3D thermal interfaces. |
Tuesday, March 16, 2021 12:54PM - 1:30PM Not Participating |
F55.00006: Phase-controlled Thermal Transport in Mesoscopic Superconducting Structures and Nanoscale Devices Invited Speaker: Francesco Giazotto The emerging field of phase-coherent caloritronics (from the Latin word calor, heat) [1] is based on the possibility of controlling heat currents by using the phase difference of the superconducting order parameter. The goal is to design and implement thermal devices that can control energy transfer with a degree of accuracy approaching that reached for charge transport by contemporary electronic components. This can be done by making use of the macroscopic quantum coherence intrinsic to superconducting condensates, which manifests itself through the Josephson effect and the proximity effect. Here, I will initially report the first experimental realization of a heat interferometer. We investigate heat exchange between two normal metal electrodes kept at different temperatures and tunnel-coupled to each other through a thermal device in the form of a DC-SQUID. Heat transport in the system is found to be phase dependent, in agreement with the original prediction. After this initial demonstration, we have extended the concept of heat interferometry to various other devices, implementing the first quantum `diffractor’ for thermal fluxes, realizing the first balanced Josephson heat modulator, and the first tunable 0-π thermal Josephson junction. Finally, I will conclude by showing the realization of the first phase-tunable Josephson thermal router. Thanks to the Josephson effect, this latter structure allows to regulate the thermal gradient between the output electrodes until reaching its inversion, and represents an important step towards the realization of caloritronic logic components, and quantum thermal machines. |
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