Seminars Archive

Twist Angle Effects on the Electronic Structure of WS2 and Graphene

Abstract
Twisted bilayer materials, such as graphene and transition metal dichalcogenides like WS2, have attracted significant attention due to their rich emergent properties. Despite their promise for uncovering novel physical phenomena, making them at scales large enough for detailed spectroscopic analysis remains a challenge. As a result, direct measurements of their electronic structures using angle-resolved photoemission spectroscopy (ARPES) have been limited. In this talk, I will present recent nanoscale ARPES measurements on twisted bilayer WS2 with a twist angle of 4.4°, and twisted bilayer graphene with a 2.4° twist angle. For WS2, comparison with density functional theory (DFT) calculations along key symmetry directions reveals unexpected effects due to structural relaxation [1]. In graphene, we observe clear signatures of modifications to the electronic structure at the M point, well below the Fermi level, which is possibly a consequence of the twisting. These results shed new light on the complex behavior of twisted bilayer materials and suggest promising directions for future research.

[1] G. Feraco, O. De Luca, P. Przybysz, H. Jafari, O. Zheliuk, Y. Wang, P. Schädlich, P. Dudin, J. Avila, J. Ye, T. Seyller, P. Dabrowski, P.J. Kowalczyk, J. Slawinska, P. Rudolf, A.a Grubisic-Cabo. Phys. Rev. Mat. 8 (2024)