Orbital doublet driven even-spin Chern insulators

Abstract

Quantum spin Hall insulators hosting edge spin currents hold great potential for low-power spintronic devices. In this paper, we present a universal approach to achieve a high and near-quantized spin Hall conductance plateau within a sizable bulk gap. Using a nonmagnetic four-band model Hamiltonian, we demonstrate that an even-spin Chern (ESC) insulator can be accessed by tuning the sign of spin-orbit coupling (SOC) within a crystal symmetry-enforced orbital doublet. With the assistance of a high spin Chern number of $C_S=-2$ and spin $U$(1) quasisymmetry, this orbital-doublet-driven ESC phase is endowed with the near-double-quantized spin Hall conductance. We identify 12 crystallographic point groups supporting such a sign-tunable SOC. Furthermore, we apply our theory to realistic examples, and show the phase transition from a trivial insulator governed by positive SOC in the RuI${}_3$ monolayer to an ESC insulator dominated by negative SOC in the RuBr${}_3$ monolayer. This orbital-doublet-driven ESC insulator, RuBr${}_3$, showcases nontrivial characteristics including helical edge states, near-double-quantized spin Hall conductance, and robust corner states. Our work provides different pathways in the pursuit of the long-sought quantum spin Hall insulators.

8 pages, 7 figures

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Cited by in corpus (5)

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• Atomically thin obstructed atomic insulators with robust edge modes and quantized spin Hall effect
• Tunable Competing Electronic Orders in Double Quantum Spin Hall Superlattices
• Engineering Majorana Kramers Pairs In Synthetic High Spin Chern Insulators
• Physical Pictures for Quasisymmetry in Crystals