Quantum Spin Hall Materials

Abstract

The quantum spin Hall (QSH) effect describes the state of matter in certain 2D electron systems, in which an insulating bulk state arises together with helical states at the edge of the sample. In stark contrast to its closest kin, the integer quantum Hall state, the QSH state exists only in time‐reversal symmetric system (e.g., in non‐magnetic materials and without the application of external magnetic field). This article reviews the development of the understanding and construction of the QSH states after their first theoretical proposal, with an emphasis on the materials perspective. Certain semiconductor quantum wells and 2D materials with strong spin–orbit coupling have been found to support QSH states.

2024 roadmap on 2D topological insulators

“…We note that this roadmap is not meant as a comprehensive review article, but rather as a status update, surveying material systems, materials challenges, and possible device realizations. For excellent reviews and perspectives on 2D TI materials and theory, we refer the reader to the following (non-exhaustive) list of reviews [1,[33][34][35][36][37][38]. We are aware that several promising materials candidates, characterization techniques, or application aspects may have not been covered, or not been covered to sufficient detail, yet we hope that this roadmap gives an illustrative overview of current progress and challenges in the field.…”

Tendency of Gap Opening in Semimetal 1T′‐MoTe2 with Proximity to a 3D Topological Insulator

“…Thus, intensive studies have always been carried out to explore or design candidates with large band gap QSH effects both in theories and experiments. [10][11][12][13][14][15][16][17][18][19] The family of the transition metal dichalcogenides MX 2 (M = Mo, W; X = S, Se, and Te) in the 1T′ phase (i.e., 1T′-MX 2 ) is a fascinating class of QSH insulators. [11,14,[16][17][18][19][20][21][22][23] Among these materials, 1T′-WTe 2 was the first case proved to possess a QSH band gap of ≈55 meV, and the QSH effect up to 100 K was observed in its simple monolayer (ML) form.…”

“…[10][11][12][13][14][15][16][17][18][19] The family of the transition metal dichalcogenides MX 2 (M = Mo, W; X = S, Se, and Te) in the 1T′ phase (i.e., 1T′-MX 2 ) is a fascinating class of QSH insulators. [11,14,[16][17][18][19][20][21][22][23] Among these materials, 1T′-WTe 2 was the first case proved to possess a QSH band gap of ≈55 meV, and the QSH effect up to 100 K was observed in its simple monolayer (ML) form. [14,16,24] In addition, the QSH insulating features of ML 1T′-WSe 2 were verified by angle resolved photo emission spectroscopy (ARPES) as well as by scanning tunneling spectroscopy (STS).…”

Topology, flat bands and magnetic fields in artificial electronic lattices

“…De intrinsieke spin-baankoppeling in grafeen is echter te klein om dit gewilde effect waar te nemen [2,3]. Hoewel er veel pogingen zijn gedaan om de intrinsieke spin-baankoppeling in grafeen te verbeteren, zoals door het toevoegen van zware atomen [4,5], zijn de resultaten tot op heden niet overtuigend [6].…”

“…However, in graphene the intrinsic spin orbit-coupling is much too small to observe this highly desired property [2,3]. Although many attempts have been made to enhance the intrinsic spin-orbit coupling in graphene, like adding heavy atoms [4,5], the results are not yet conclusive [6].…”