Regensburg 2025 – scientific programme
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DS: Fachverband Dünne Schichten
DS 3: 2D Materials and their Heterostructures I (joint session DS/HL)
DS 3.6: Talk
Monday, March 17, 2025, 16:30–16:45, H3
Pressure-dependent Effective Hamiltonian and Topological Transitions for Twisted Bilayer Transition Metal Dichalcogenides — •Miftah Hadi Syahputra Anfa1, Sabri Elatresh1,2, Hocine Bahlouli1,3, and Michael Vogl1,2 — 1Physics Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia — 2Interdisciplinary Research Center (IRC) for Intelligent Secure Systems, KFUPM, Dhahran, Saudi Arabia — 3Interdisciplinary Research Center (IRC) for Advanced Materials, KFUPM, Dhahran, Saudi Arabia
Recent studies have shown the existence of nontrivial topological moire bands in twisted bilayer transition metal dichalcogenides (TMDs), which depend on the twist angle. Motivated by this, we present a study of such a system under applied vertical pressure. The study begins by first considering the untwisted bilayer case without pressure. We find that the system can be described by an effective low-energy Hamiltonian that behaves approximately quadratic and includes layer-shift dependent terms that we were able to determine by symmetry. The structure is then relaxed under pressure in the 0.0 - 3.5 GPa range using ab initio density functional theory (DFT). The DFT band structures for each corresponding pressure are fitted to the effective Hamiltonian to obtain the pressure-dependent parameters. Consecutively, the explicit expression for the twisted pressure-dependent Hamiltonian is obtained by treating the twist as a position-dependent shift between layers. We then present changes in Chern number results for the important energy bands due to pressure.
Keywords: moiré material; topological insulator; transition metal dichalcogenides