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 S59: Thermodynamic and Transport Properties (not QHE, FQHE)Live
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Sponsoring Units: FIAP Chair: Xuan Gao, Case Western Reserve University |
Thursday, March 18, 2021 11:30AM - 11:42AM Live |
S59.00001: Autonomous quantum absorption refrigerators Etienne Jussiau, Sreenath Kizhakkumpurath Manikandan, Andrew N Jordan We propose a new design for a quantum absorption refrigerator using resonant-tunneling quantum dots. A hot and cold fermionic leads are connected to a very hot central cavity via quantum dots and we analyze situations where the heat from the cavity is absorbed to power a heat current from the cold lead to the hot one. We infer the conditions under which the device operates as refrigerator and identify two distinct regimes where cooling is possible depending on the positions of dot energies (above or below the Fermi energy) which we link to either electron or hole transport. We further study the coefficient of performance and cooling power of the refrigerator which we optimize fine-tuning the energies and level widths of the dots. We identify the thermodynamically reversible energy configurations where the device is Carnot efficient while its cooling power vanishes, and we show that refrigeration is only possible for small values of the level width. Finally, we propose associating an arbitrary number of such refrigerators in series so as to extract heat from various reservoirs at once. We demonstrate how to use this setup for thermal control, that is, how to choose dot energies so that heat currents across the chain match a preassigned spatial distribution. |
Thursday, March 18, 2021 11:42AM - 11:54AM Live |
S59.00002: Origin of anomalous temperature dependence of Nernst effect in narrow-gap semiconductors Ryota Masuki, Takuya Nomoto, Ryotaro Arita Based on the Boltzmann transport theory, we study the origin of the anomalous temperature dependence of the Nernst coefficient (ν) due to the phonon-drag mechanism. For narrow-gap semiconductors, we find that there are two characteristic temperatures at which a noticeable peak structure appears in ν. Contrarily, the Seebeck coefficient (S) always has only one peak. While the breakdown of the Sondheimer cancellation due to the momentum-dependence of the electron relaxation time is essential for the peak in ν at low T, the contribution of the valence band to the phonon-drag current is essential for the peak at higher T. By considering this mechanism, we successfully reproduce ν and S of FeSb2 for which a gigantic phonon-drag effect is observed experimentally. |
Thursday, March 18, 2021 11:54AM - 12:06PM Live |
S59.00003: Nonreciprocal transport in Landau-Zener problem Sota Kitamura, Naoto Nagaosa, Takahiro Morimoto Responses of quantum materials against external stimuli show a rich variety according to the symmetries of the underlying microscopic Hamiltonian. In particular, nonreciprocal response with a directional transport is an important class of phenomena, which can emerge in noncentrosymmetric materials. As typified in Onsager’s reciprocal relation, however, the presence of the time-reversal symmetry sometimes forbids the directionality. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S59.00004: Origin of micron-scale propagation lengths of heat-carrying acoustic excitations in amorphous silicon Taeyong Kim, Jaeyun Moon, Austin Minnich The heat-carrying acoustic excitations of amorphous silicon are of interest because their mean free paths may approach micron scales at room temperature. Despite extensive investigation, the origin of the weak acoustic damping in the heat-carrying frequencies remains a topic of debate. Here, we report measurements of the frequency-dependent mean free path in amorphous silicon thin films from $\sim 0.1-3$ THz and over temperatures from 60 - 315 K using picosecond acoustics and transient grating spectroscopy. The mean free paths are independent of temperature and exhibit a Rayleigh scattering trend over most of this frequency range. The observed trend is inconsistent with the predictions of numerical studies based on normal mode analysis but agrees with diverse measurements on other glasses. The micron-scale MFPs in amorphous Si arise from the absence of Akhiezer and two-level system damping in the sub-THz frequencies, leading to heat-carrying acoustic excitations with room-temperature damping comparable to that of other glasses at cryogenic temperatures. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S59.00005: Photoluminescence mapping and time-domain thermo-photoluminescence for rapid imaging and measurement of thermal conductivity of boron arsenide Shuai Yue, Geethal Amila Gamage, Mohammadjavad Mohebinia, David Mayerich, Vishal Talari, Yu Deng, Fei Tian, SHENYU DAI, Haoran Sun, Viktor G. Hadjiev, Wei Zhang, Guoying Feng, Jonathan Hu, Dong Liu, Zhiming Wang, Zhifeng Ren, Jiming Bao Cubic boron arsenide (BAs) is attracting greater attention owing to the ultrahigh thermal conductivity κ higher than 1000 W/m●K. However, its bandgap has not been settled and a simple yet effective method to probe its crystal quality is missing. Furthermore, traditional κ measurement methods are destructive and time-consuming, thus they cannot meet the urgent demand for fast screening of high κ materials. After we experimentally established 1.82 eV as the indirect bandgap of BAs and observed room-temperature band-edge photoluminescence, we developed two new optical techniques that can provide rapid and non-destructive characterization of κ with little sample preparation: photoluminescence mapping and time-domain thermo-photoluminescence (TDTP). PL-mapping provides a nearly real-time image of crystal quality and κ over mm-sized crystal surfaces; while TDTP allows us to pick up any spot on the sample surface and measure its κ using nanosecond laser pulses. These new techniques reveal that the apparent single crystals are not only nonuniform in κ. Because PL-mapping and TDTP are based on the band-edge PL and its dependence on temperature, they can be applied to other semiconductors, thus paving the way for rapid identification and development of high-κ semiconducting materials. |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S59.00006: Magnetic cooling of electrons to 311 μK in a cryo-free dilution refrigerator Mohammad Samani, Christian Scheller, Nikolai Yurttagul, Kestutis Grigoras, Omid Sharifi Sedeh, Alexander Jones, Richard Haley, Jonathan R Prance, Mika Prunnila, Dominik Zumbuhl Magnetic cooling has the potential to reduce electrons' temperature in a nanostructure far below dilution refrigerator's base temperature. Cooling materials to such levels, analogous to using a more powerful microscope, enables the investigation of interesting novel physics such as exotic quantum phases, new topological quasiparticles and unprecedented quantum coherence in transport experiments. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S59.00007: Enhanced thermal Hall effect in nearly ferroelectric insulators Jing-Yuan Chen, Steven Allan Kivelson, Xiao-Qi Sun In the context of recent experimental observations of an unexpectedly large thermal Hall conductivity, κH, in insulating La2CuO4 (LCO) and SrTiO3 (STO), we theoretically explore conditions under which acoustic phonons can give rise to such a large κH. Both the intrinsic and extrinsic contributions to κH are large in proportion to the dielectric constant, ε, and the “flexoelectric” coupling, F. While the intrinsic contribution is still orders of magnitude smaller than the observed effect, an extrinsic contribution proportional to the phonon mean-free path appears likely to account for the observations, at least in STO. We predict a larger intrinsic κH in certain insulating perovskites. |
Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S59.00008: Learning electron scattering parameters by analyzing thermoelectric data Anooja Jayaraj, Ilaria Siloi, Marco Fornari, Marco Buongiorno Nardelli The theoretical prediction of thermoelectric (TE) transport properties has made systematic use of the constant relaxation time approximation (CRTA), thus ignoring effects associated with the specific scattering mechanisms at work. The idea of improving the design of TE materials through scattering engineering is very powerful. Here we investigate the role of the CRTA in the electronic properties of well-known TE materials, by considering scattering models with energy and temperature dependence. The introduction of a self-consistent fitting procedure allows the existing models to be finely tuned for the individual experimental sample and, the contribution of each mechanism to be singled out without relying on experimental parameters. Transport coefficients, scattering models, and the fitting procedure have been computed with the recently developed PAOFLOW software (http://aflowlib.org/src/paoflow/). |
Thursday, March 18, 2021 1:06PM - 1:18PM Live |
S59.00009: Exciton condensation in 2D WSe2/InSe electric double layers Brian Holler, Arvind Shankar Kumar, Xuan Gao Exciton effects in two-dimensional (2D) materials are becoming more relevant to our understanding of photonic and optoelectronic devices. 2D transition metal dichalcogenides (TMDs), such as WSe2, exhibit large exciton binding energies and have the flexibility of creating unique stacked heterostructures with other 2D materials in order to explore exciton condensation and other condensate-based applications. In this study we plan to illustrate the presence of interlayer excitons electrically formed between stacked layers of WSe2 and InSe. We are able to confirm these electron-hole pairs via gate-induced tunnelling characteristics at varying bias voltages which can be compared to correlated electron-hole pair tunnelling characteristics. This study opens up the motivation and opportunity for other unique 2D heterostructure stacks to be probed for exciton condensation and advance exciton-based technologies. |
Thursday, March 18, 2021 1:18PM - 1:30PM Live |
S59.00010: Effect of the polar distortion on the thermoelectric properties of GeTe Aida Sheibani, Charles Paillard, Abhyian Pandit, Raad E Haleoot, Laurent Bellaiche, Bothina Hamad First principle calculations are performed to investigate the effect of polar order strength on the thermoelectric properties of GeTe alloy in its rhombohedral structure. Different magnitudes of polarization exhibit a noticeable effect on the thermoelectric properties of GeTe. In particular, polar structures with higher polarization tend to show higher thermoelectric efficiencies. Thus, it is shown that polarization engineering is an important factor in designing efficient thermoelectric devices. In particular, we proposed that high thermoelectric performances could be achieved by growing epitaxial GeTe films that are bi-axially compressed in the directions perpendicular to the polar axis in order to achieve larger polarization states. |
Thursday, March 18, 2021 1:30PM - 1:42PM Live |
S59.00011: Thermopower and Electrical Transport in Ag2-δTe under Magnetic Field Ian Leahy, Peter Siegfried, Harold Schnyders, Anke Husmann, Minhyea Lee We investigate the magnetotransport and thermopower properties in a series of the silver deficient semiconductors Ag2-δTe (δ = 0, 2×10-4, and 7×10-4). We find that the non-trivial field dependences of both the longitudinal and transverse thermoelectric coefficients are sufficiently described by simple expressions that are parameterized with the tangent of the hall angle, defined as tan θH ≡ ρxy/ρxx. While our model is based on the semiclassical transport theory for a single band, it captures intertwined transport characteristics in an explicit manner. We expect our model to have broad applicability in understanding thermoelectric responses as well as electrical transport under high magnetic field in other semimetals and semiconductors. |
Thursday, March 18, 2021 1:42PM - 1:54PM Live |
S59.00012: Thermal transport from nanostructured heat sources on diamond probed using coherent extreme ultraviolet beams Brendan McBennett, Joshua L Knobloch, Begoña Abad, Travis D Frazer, Albert Beardo, Lluc Sendra, Juan Camacho, Javier Bafaluy, Weilun Chao, roger falcone, Jorge Nicolas Hernandez Charpak, Henry C Kapteyn, Xavier Alvarez, Margaret Murnane Nanostructured materials can exhibit properties unattainable in bulk materials, with applications in next-generation energy efficient devices. However, macroscopic, diffusive transport models break down at length scales comparable to the mean free path of a material’s dominant heat carriers. Moreover, there are few characterization techniques that can probe functional nanosystems. Here, we use short wavelength (~30nm), ultrafast (~10fs) extreme ultraviolet (EUV) beams to nondestructively probe thermal transport away from nanoscale heat sources on diamond. Diamond is a promising material for diodes, high strength coatings, and integrated circuits—and is of special interest for quantum communication and memory. We impulsively heat nickel nano-gratings fabricated on a diamond substrate with an infrared pump laser and quantify the heat transport efficiency by monitoring the surface deformation using a time-delayed EUV probe. We use our experimental results to develop and validate a predictive hydrodynamic transport model and investigate the respective roles played by diamond’s intrinsic scattering environment and the nickel-diamond interface. Additionally, we spatially analyze non-diffusive cooling processes using individual diffracted orders in the scattered EUV probe. |
Thursday, March 18, 2021 1:54PM - 2:06PM On Demand |
S59.00013: Unusual anisotropic thermal expansion in
multilayer SnSe leads to positive-to-negative
crossover of Poisson’s ratio Yu-Tian Zhang, Rui-Zi Zhang, Jian Liu, Yu-Yang Zhang, Shixuan Du, Sokrates T Pantelides An unusual anisotropic thermal expansion occurs in monolayer SnSe when it is subjected to heating, i.e., the long lattice constant contracts, and the short one expands, causing a rectangular-to-square-lattice phase transition at a critical temperature (Tc). An even more prominent monolayer-to-bulk thermal-expansion behavior has been discovered by density-functional-theory calculations combined with Grüneisen’s theory within the quasiharmonic approximation[1]. The unusual thermal expansion survives in multilayer SnSe, while the thermal expansion coefficients of different layers are almost unchanged. This phenomenon can be explained by a delicate balance between the elastic stiffness coefficient and Grüneisen parameters. Finally, the Poisson’s ratio of multilayer SnSe decreases at elevated temperatures and turns negative, indicating a crossover point of diminished Poisson’s ratio at some intermediate temperature. These findings provide not only new understanding of the thermal properties of monochalcogenides, but also a feasible approach to design zero-Poisson’s-ratio materials. |
Thursday, March 18, 2021 2:06PM - 2:18PM On Demand |
S59.00014: Predictive theory of charge transport in perovskite oxides Jin-Jian Zhou, Marco Bernardi Quantitatively predicting charge transport properties and the dominant carrier scattering mechanisms in transition metal oxides remains an open problem, partially because of the complex interplay between electrons and lattice vibrations in these materials. Noteworthy challenges for theory include accounting for soft phonon modes due to structural phase transitions and polaron effects due to strong electron-phonon coupling. Using ab initio approaches we recently developed [1], we address these challenges and compute the phonon-limited transport properties in a wide range of perovskite oxides, including KTaO3, BaZrO3, BaHfO3, SrTiO3, BaSnO3, and SrSnO3. We investigate in detail the charge transport mechanisms, the role of the band structure and spin-orbit coupling, polaron effects, and the contribution to transport from different phonon modes. Our analysis provides materials design rules for the carrier mobility in perovskite oxides. |
Thursday, March 18, 2021 2:18PM - 2:30PM Not Participating |
S59.00015: Towards Ponderomotive Trapping and Guiding Charge Carriers in Semiconductors Damon Daw, Artur Lozovoi, Yunhan Wang, YunHeng Chen, Ayesha Lakra, Marcus Doherty, Carlos Meriles Understanding charge transport dynamics in semiconductors is a research area of profound technological and fundamental interest. The miniaturization of semiconductor electronics demands precise control of carrier transport, which in turn requires precise experimental techniques to characterize the microscopic interactions that influence transport. Here, we present a novel, non-invasive method for spatially confining and measuring transport characteristics of charge carriers in covalent semiconductors using ponderomotive potentials similar to those used in traditional ion trapping experiments. While trapping charged particles in vacuum has been thoroughly studied for decades, trapping and guiding mobile charges inside a solid presents unique challenges. The anisotropy of effective masses, phonon scattering and the presence of crystal impurities may act to destabilize the trap. However, we show that these processes can not only be mitigated in order to realize stable trapping or guiding of charge carriers, but the confined carriers can serve as a unique probe to measure these phenomena. |
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