Dual quantum spin Hall insulator by density-tuned correlations in TaIrTe4

Jian Tang, Thomas Siyuan Ding, Hongyu Chen, Anyuan Gao, Tiema Qian, Zumeng Huang, Zhe Sun, Xin Han, Alex Strasser, Jiangxu Li, Michael Geiwitz, Mohamed Shehabeldin, Vsevolod Belosevich, Zihan Wang, Yiping Wang, Kenji Watanabe, Takashi Taniguchi, David C. Bell, Ziqiang Wang, Liang Fu, Yang Zhang, Xiaofeng Qian, Kenneth S. Burch, Youguo Shi, Ni Ni, Guoqing Chang (), Su-Yang Xu and Qiong Ma ()
Additional contact information
Jian Tang: Boston College
Thomas Siyuan Ding: Boston College
Hongyu Chen: Nanyang Technological University
Anyuan Gao: Harvard University
Tiema Qian: University of California Los Angeles
Zumeng Huang: Boston College
Zhe Sun: Boston College
Xin Han: Chinese Academy of Sciences
Alex Strasser: Texas A&M University
Jiangxu Li: University of Tennessee
Michael Geiwitz: Boston College
Mohamed Shehabeldin: Boston College
Vsevolod Belosevich: Boston College
Zihan Wang: Boston College
Yiping Wang: Boston College
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
David C. Bell: Harvard University
Ziqiang Wang: Boston College
Liang Fu: Massachusetts Institute of Technology
Yang Zhang: University of Tennessee
Xiaofeng Qian: Texas A&M University
Kenneth S. Burch: Boston College
Youguo Shi: Chinese Academy of Sciences
Ni Ni: University of California Los Angeles
Guoqing Chang: Nanyang Technological University
Su-Yang Xu: Harvard University
Qiong Ma: Boston College

Nature, 2024, vol. 628, issue 8008, 515-521

Abstract: Abstract The convergence of topology and correlations represents a highly coveted realm in the pursuit of new quantum states of matter1. Introducing electron correlations to a quantum spin Hall (QSH) insulator can lead to the emergence of a fractional topological insulator and other exotic time-reversal-symmetric topological order2–8, not possible in quantum Hall and Chern insulator systems. Here we report a new dual QSH insulator within the intrinsic monolayer crystal of TaIrTe4, arising from the interplay of its single-particle topology and density-tuned electron correlations. At charge neutrality, monolayer TaIrTe4 demonstrates the QSH insulator, manifesting enhanced nonlocal transport and quantized helical edge conductance. After introducing electrons from charge neutrality, TaIrTe4 shows metallic behaviour in only a small range of charge densities but quickly goes into a new insulating state, entirely unexpected on the basis of the single-particle band structure of TaIrTe4. This insulating state could arise from a strong electronic instability near the van Hove singularities, probably leading to a charge density wave (CDW). Remarkably, within this correlated insulating gap, we observe a resurgence of the QSH state. The observation of helical edge conduction in a CDW gap could bridge spin physics and charge orders. The discovery of a dual QSH insulator introduces a new method for creating topological flat minibands through CDW superlattices, which offer a promising platform for exploring time-reversal-symmetric fractional phases and electromagnetism2–4,9,10.

Date: 2024
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DOI: 10.1038/s41586-024-07211-8

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