Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session M04: Properties of Multi-Moiré MaterialsFocus
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Sponsoring Units: DMP Chair: Apurba Paul, University of Notre Dame Room: L100D |
Wednesday, March 6, 2024 8:00AM - 8:12AM |
M04.00001: Artificial intelligence for artificial materials: moiré atoms Di Luo, Aidan Reddy, Trithep Devakul, Liang Fu Semiconductor moiré materials have emerged as a pivotal experimental platform for realizing novel strongly-correlated states of matter, providing new opportunities for designing artificial quantum materials. Despite its importance, understanding the many strongly-correlated electron physics in these systems is challenging due to the limited accuracy and scalability of the conventional methods. In this work, we propose a new approach of integrating multi-scale modeling with artificial intelligence to investigate the artificial quantum materials. We study the regime that the system can be modeled as an array of ``moiré atoms”, each of which consists of several strongly-correlated electrons confined to a moiré superlattice potential minimum. We develop a scalable method with a state-of-the-art 2D fermionic neural network to accurately simulate the physics. We find that strong Coulomb interactions in combination with the anisotropic moiré potential lead to striking ``Wigner molecule", which charge density distributions can be observed with scanning tunneling microscopy. |
Wednesday, March 6, 2024 8:12AM - 8:24AM |
M04.00002: Multiscale lattice relaxation and topological 1D state in twisted trilayer graphene Naoto Nakatsuji, Takuto Kawakami, Mikito Koshino We present comprehensive theoretical studies on the lattice relaxation and the electronic structures in general nonsymmetric twisted trilayer graphenes. By using an effective continuum model, we show that the relaxed lattice structure forms a patchwork of moiré-of-moiré domains, where a moiré pattern given by layer 1 and 2 and another pattern given by layer 2 and 3 become locally commensurate. The atomic configuration inside the domain exhibits a distinct contrast between chiral and alternating stacks, which are determined by the relative signs of the two twist angles. In the chiral case, the electronic band calculation reveals a wide energy window (>50 meV) with low density of states, featuring sparsely distributed highly one-dimensional electron bands. These one-dimensional states exhibit a sharp localization at the boundaries between supermoiré domains, and they are identified as a topological boundary state between distinct Chern insulators. The alternating trilayer exhibits a coexistence of the flat bands and a monolayerlike Dirac cone, and it is attributed to the formation of moiré-of-moiré domains equivalent to the mirror-symmetric twisted trilayer graphene. |
Wednesday, March 6, 2024 8:24AM - 8:36AM |
M04.00003: Correlation between Heat Flow and Electrical Current across Four-layered MoS2 Kan Ueji, Kaiyao Zhou, Takuma Shiga, Sota Nakamura, Hiroyuki Nishidome, Takashi Yagi, Yohei Yomogida, Takahiro Yamamoto, Yasumitsu Miyata, Kazuhiro Yanagi Artificially stacked transition metal dichalcogenide (MX2) films show ultra-low thermal conductance along out-of-plane directions. The ultra-low thermal conductance is attractive for thermoelectric energy conversion. However, the relationships between out-of-plane heat and electrical conductivity across MX2 films are still under debate because of the limitations of the measurement techniques. A time-domain thermoreflectance (TDTR) method is one of the techniques that can determine the thermal conductivity of thin films in the out-of-plane direction. In conventional TDTR setups, Al is used as the thermal transducer, but we developed a TDTR system where Au is used as a thermal transducer (Au-TDTR). Au can be also used as electrodes to evaluate the electrical characteristics of the sample. In this study, we investigated out-of-plane heat and electrical characteristics of four-layered (4L) MoS2 films with different interfacial coupling by annealing process. |
Wednesday, March 6, 2024 8:36AM - 9:12AM |
M04.00004: Twisted bi-layer graphene: magic range behavior and implications, a first-principles perspective Invited Speaker: Efthimios Kaxiras The physics of twisted bi-layer and multi-layer graphene continues to be of great interest in understanding strongly correlated electron states, with many details still unclear, and a simple phenomenological model still lacking. The moiré pattern observed experimentally in twisted bilayer graphene (tBLG) clearly shows the formation of different types of domains. These domains can be explained by the atomic relaxation, both in-plane and out-of-plane, using continuum elasticity theory and the Generalized Stacking Fault Energy (GSFE) concept. Moreover, the atomic relaxation significantly affects the electronic states, leading to a pair of flat bands at the charge neutrality point which are separated by band gaps from the rest. These features appear for a small range of twist angles, that we call the “magic range”, around the twist angle of 1o. We discuss how all these aspects of the system are crucial for understanding the origin of correlated states and superconductivity in tBLG. We also present a minimal model that can capture these features with 2 flat and 2 auxiliary bands and explore the implications of the model for correlated electron behavior in the context of the Hubbard model. |
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