Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Q42: 2D Materials: Advanced Characterization IVFocus
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Sponsoring Units: DMP Chair: Christopher Smallwood, San Jose State University Room: Room 318 |
Wednesday, March 8, 2023 3:00PM - 3:36PM |
Q42.00001: Tunneling Probe of Magnons in 2D Alpha-RuCl3 Invited Speaker: Adam Wei Tsen I will discuss our recent results using tunneling spectroscopy to probe the underlying magnetic order and excitations in the Kitaev material alpha-RuCl3 in monolayer form. We find a reversal of the magnetic anisotropy together with an enhancement of the Kitaev interaction due to picoscale structural distortions. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q42.00002: Mapping the Thermoelectric Properties of Noble Transition Metal Dichalcogenides at Atomic Scale Saban M Hus, An-Ping Li, Yong P Chen, Lina Liu Scanning tunneling microscope (STM) provides a unique platform to characterize electronic, magnetic and thermal properties of atomic scale heterogeneities in 2D materials. Among these properties, the thermoelectric power is particularly interesting due to its high sensitivity to the density of states around Fermi level. Recently, it was predicted that monolayer noble transition metal dichalcogenides (TMDs) with hexagonal lattice structure are high performance thermoelectric materials at room temperature with their pentagonal counterparts promising even better performance due to the in-plane anisotropy of the lattice. However, the thermoelectric properties of these materials can significantly be altered by the heterogeneities in the atomically thin layers. Using a STM, we investigate the thermoelectric properties of both pentagonal and hexagonal noble-TMD monolayers in atomic resolution. We observe that atomic-scale defects like single chalcogenide vacancies and inhomogeneities in 2D layer-substrate interface create a rich thermoelectric landscape which is invisible to mesoscopic scale measurements. Detailed understanding and precise control of these heterogeneities can lead to next-generation thermoelectric materials for energy applications. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q42.00003: Thermoelectric properties of two-dimensional MoS2 semiconductors in a wide temperature range Wen-Bin Jian, Chetan Awasthi, Kuan-Cheng Lu, S. S. Islam Although the hopping transport in thermoelectric (TE) power and conductance of single-layer MoS2 was experimentally studied, the relation between the disorder parameter and the TE power was not investigated yet. Nor did the conduction mechanism at temperatures above 450 K be studied regarding to the TE power. Further, the TE power factor was essential for the applications while its temperature, layer thickness, and carrier concentration dependences were not completely explored yet. Here we will report the fabrication of both TE and field-effect transistor devices based on MoS2 flakes with a thickness from single layer to 39 layers. In particular, the TE properties of the two-dimensional MoS2 semiconductor are studied in a wide temperature range from 80 to 600 K. We will talk about the intrinsic disorder effects on the TE power and electron transport at temperature below 200 K. At temperatures ranging from 300 to 450 K, we will investigate thermal activation and discuss its effects on the TE power. In addition, at temperatures above 450 K, we will show an extrinsic effect which comes from the interface between the MoS2 flake and the SiO2 dielectric layer. The extrinsic effect leads to a memory effect while it offers an enhancement of TE power factor at high temperatures. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q42.00004: Measuring AC Conductivity of 2D Superconductors at Microwave Frequencies Mary Kreidel
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Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q42.00005: Time-Resolved ARPES Study of Floquet-Bloch States in Monolayer Tungsten Disulfide Vivek Pareek, David R Bacon, Xing Zhu, Yang-Hao Chan, Fabio Bussolotti, Nicholas S Chan, Joel P Urquizo, Kenji Watanabe, Takashi Taniguchi, Michael K Man, Julien Madéo, Diana Y Qiu, Kuan Eng Johnson Goh, Felipe H da Jornada, Keshav M Dani Floquet engineering of the band structure has attracted much interest recently. This is usually achieved by using an intense light field to drive the system out of equilibrium and gain access to novel quantum effects, such as Floquet-Bloch states in a topological insulator, which is otherwise inaccessible in the equilibrium condition [1–3]. Time-resolved ARPES (Tr-ARPES) has been at the forefront of studying these emergent phenomena in various quantum materials such as Bismuth selenide and bulk Tungsten diselenide [1,2,4]. Here we report the observation of Floquet-Bloch states in monolayer Tungsten Disulfide using Tr-ARPES. We further discuss the impact of the driving field on the band structure. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q42.00006: Mechanically reconfigurable quantum devices in a van der Waals heterostructures Ian Sequeira, Andrew Barabas, yuhui yang, Aaron Barajas, Kenji Watanabe, Takashi Taniguchi, Javier D Sanchez-Yamagishi Nanoscale electronic devices are generally static, with the material structure and geometry set during the fabrication process. In contrast, the unique low interfacial friction present in van der Waals (vdW) materials has been utilized to dynamically reconfigure layer overlap and orientation in vdW heterostructures to strongly modify its structure and physical properties in-situ. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q42.00007: Real-time In-situ Electrostatic Alignment for Micro and Nano ARPES: First results Daniel A Beaton, Craig Polley, Timo Wätjen, Marcus Lundwall, Khadiza Ali, Patrik Karlsson High quality ARPES measurements, particularly micro/nanoARPES, require highly optimized alignment of the excitation photon beam, sample, and analyzer focal point. Scienta Omicon's new DFS30 spectrometer (patent pending) simplifies this alignment by employing electronic adjustment of the analyzer focal point. In this presentation we will show the first results from our ground-breaking real-time and in-situ Electrostatic 3D Focus Adjustment technology. By replacing imprecise mechanical movements with precise electrostatic adjustments of the lens tables users are able to greatly improve data quality and repeatability in ARPES measurements, as well as providing significantly improved workflow, speed, and reproducibility when optimizing experimental conditions. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q42.00008: Spin-orbit coupling-induced magnetic phases in the rhombohedral trilayer graphene. Yaroslav Zhumagulov, Denis Kochan, Jaroslav Fabian We study the effect of proximity-induced intrinsic and Rashba spin-orbit coupling on the magnetic phase diagram of rhombohedral trilayer graphene (RTG). The magnetic phase diagram of RTG is calculated in the parametric space of an external electric field and the electron doping level for several sets of spin-orbit coupling parameters corresponding to the proximity effect of real substrates. In our calculations, RTG without spin-orbit coupling has two magnetic phases, such as interlayer antiferromagnetic ordering or intervalley antiferromagnetic ordering. It has been found that the introduction of a spin-orbit coupling into RTG significantly affects its magnetic phase diagram. Spin-orbit coupling causes splitting between magnetic phases into phases with out-of-plane or in-plane spin ordering. Finally, we calculated the dependence of the RTG magnetic ordering at a fixed level of electron doping and an external electric field on the amplitude of intrinsic spin-orbit coupling. We discuss a possibility of a significant modification of the RTG magnetic ordering by the design of the van der Waals heterostructure and proximity-induced spin-orbit coupling. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q42.00009: Layer-by-layer disentanglement of Bloch states via frequency-domain photoemission Woojoo Lee, Sebastian Fernandez-Mulligan, Hengxin Tan, Chenhui Yan, Yingdong Guan, Seng Huat Lee, Ruobing Mei, Chaoxing Liu, Binghai Yan, Zhiqiang Mao, Shuolong Yang We report a layer-encoded frequency-domain ARPES experiment on a magnetic topological insulator (MnBi2Te4)(Bi2Te3) to characterize the layer origins of electronic states. Infrared laser excitations launch coherent lattice vibrations with the layer index encoded by the vibration frequency; photoemission spectroscopy tracks the electron dynamics, where the layer information is decoded in the frequency domain. This layer-frequency correspondence reveals a surprising wavefunction relocation of the topological surface state from the top magnetic layer into the buried second layer, reconciling the controversy over the vanishing broken-symmetry energy gap in (MnBi2Te4)(Bi2Te3) and its related compounds. The layer-frequency correspondence can be harnessed to disentangle electronic states layer-by-layer in a broad class of van der Waals superlattices. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q42.00010: Magnetothermal conductivity of Ta2NiSe5 at low temperatures Vikram Nagarajan, Luke Pritchard Cairns, James Analytis Ta2NiSe5 (TNS) has been intensely studied due to its supposed proximity to the coveted excitonic insulator state. While a variety of experimental techniques such as Raman spectroscopy, NMR/Knight shift, and transport have lended support to the excitonic insulator claim, there have since been recent ARPES and diffuse X-ray scattering results that suggest the features of TNS are due to strong electron-lattice coupling and lattice fluctuations. Nonetheless, the bulk of these studies focus on the transition at Tc = 329 K; few studies have explored the low temperature behavior of this material. Several studies have noted certain features below 100 K, such as an upturn in magnetic susceptibility, suppressed electronic activation energy, and a suppression of the thermopower. It is not yet clear whether these features are intrinsic to the sample or due to impurities, nor is it clear whether they are related to any exciton physics. Here, we present low-temperature magnetothermal conductivity measurements on TNS in order to clarify the quasiparticle behavior as well as the underlying cause of these features. |
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