Atomic monolayers as 2D topological quantum materials

Date

Jun 2, 2025

Time

4:30 PM - 5:30 PM

Speaker

Prof. Ralph Claessen

Affiliation

Universität Würzburg

Series

MPI-PKS Kolloquium

Language

en

Main Topic

Physik

Other Topics

Physik

Description

Confining electrons to two dimensions (2D) is known to enhance electronic correlations and promote non-trivial topological phases. Atomic monolayers on semiconductor substrates represent the ultimate 2D limit of such confinement and thus have recently come into focus as "third-generation 2D designer quantum materials", following the examples of graphene and monolayer transition metal dichalcogenides. Here I will focus on atomic monolayers as 2D topological insulators (2D-TIs) which host 1D metallic and spin-polarized edge states as hallmark of the quantum spin Hall (QSH) effect. My examples range from bismuthene (Bi/SiC(0001)) [1-3], the 2D-TI with the largest band gap realized to date, to indenene (In/SiC(0001)), a triangular lattice of In atoms with emergent honeycomb physics [4,5]. Using ARPES as well as STM/STS we have studied their electronic structure and especially their topological edge states, revealing interesting insights into their protection (or loss thereof) against single-particle backscattering. I will also demonstrate how circular dichroism in ARPES can serve as a tool to identify non-trivial topology in the bulk states [6]. Finally, I will discuss the stabilization of these monolayers in ambient conditions via van der Waals capping [7,8], paving the way towards ex situ experiments and the realization of transport devices. [1] Science 357, 287 (2017) [2] Nat. Phys. 16, 47 (2020) [3] Nat. Commun. 13, 3480 (2022) [4] Nat. Commun. 12, 5396 (2021) [5] arXiv:2503.11497 [6] Phys. Rev. Lett. 132, 196401 (2024) [7] Nat. Commun. 15, 1486 (2024) [8] arXiv:2502.01592

Last modified: Jun 2, 2025, 7:35:28 AM