Van der Waals Heterostructure Pt$_{2}$HgSe$_{3}$/CrI$_3$ for Topological Valleytronics

Abstract

We identify a valley-polarized Chern insulator in the van der Waals heterostructure, Pt2HgSe3/CrI3, for potential applications with interplay between electric, magnetic, optical, and mechanical effects. The interlayer proximity magnetic coupling nearly closes the band gap of Pt2HgSe3 and the strong intra-layer spin-orbit coupling further lifts the valley degeneracy by over 100 meV leading to positive and negative band gaps at opposite valleys. In the valley with negative gap, the interfacial Rashba spin-orbit coupling opens a topological band gap of 17.8 meV, which is enlarged to 30.8 meV by adding an h-BN layer. We find large orbital magnetization in Pt2HgSe3 layer that is much larger than spin, which can induce measurable optical Kerr effect. The valley polarization and Chern number are coupled to the magnetic order of the nearest neighboring CrI3 layer, which is switchable by electric, magnetic, and mechanical means in experiments. The presence of h-BN protects the topological phase allowing the construction of superlattices with valley, spin, and layer degrees of freedoms.

Gate-tunable imbalanced Kane-Mele model in encapsulated bilayer jacutingaite

“…Even more compelling, the imbalance affects also two additional NNN spin-orbit terms: Kane-Mele [9,10] and in-plane Rashba-like [51] spin-orbit couplings. Also in this case, these terms retain values very close to the one in the monolayer for the outer sublattices [23,25,52], while they are strongly suppressed for the inner sublattices, in analogy with bulk jacutingaite, where the effect of spin-orbit coupling is almost negligible [31][32][33]. Traditionally, topological transitions were understood in terms of spin-orbit couplings that were identical on both sublattices [9,10].…”

“…In all these systems, the operating conditions where transport is dominated by edge states are limited to fairly low temperatures owing to their small bulk energy gap. A breakthrough could be represented by monolayer Pt 2 HgSe 3 , which has been predicted using first-principles simulations to be the first materials realization of the seminal Kane-Mele model [9,10] for QSHIs, with a substantial energy gap of 0.5 eV [23] (and could even give rise to a Chern insulator when functionalized [24] or interfaced with a magnetic material like CrI 3 [25]). Although monolayers of this material could be potentially exfoliated [26] from a bulk layered mineral called jacutingaite [27,28], a clear experimental validation is still lacking [29].…”