Reemergence of the Quantum Spin Hall Insulator State in TaIrTe4

Scientific Achievement

Quantum spin insulator graphic
The reemergence of the quantum spin Hall insulating state due to van Hove singularities in a monolayer of TaIrTe4.

We report two different quantum spin Hall (QSH) insulator states in monolayer TaIrTe4 that arise from the interplay of topology and density-tuned electronic correlations.

Significance and Impact

Introducing electron correlations to a QSH insulator can lead to the emergence of a fractional QSH insulator and exotic time-reversal symmetric topological order. Our finding highlights TaIrTe4 as a promising platform for exploring these phases.

Research Details

We fabricated high-quality, dual-gated monolayer TaIrTe4 devices and detected two distinct QSH states ( QSH-I and QSH-II, respectively):

  • QSH-I is a single-particle phase that occurs at charge neutrality.
  • QSH-II arises when additional electrons are injected by gating. An electronic instability near low-energy van Hove singularities (vHs) possibly leads to a topological charge density wave phase, as suggested by our theoretical investigations. 

J. Tang et al., “Dual quantum spin Hall insulator by density-tuned correlations in TaIrTe4,”  Nature 628, 515 (2024).