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Evidence of a room-temperature quantum spin Hall edge state in a higher-order topological insulator.

Nana ShumiyaMd Shafayat HossainJia-Xin YinZhiwei WangMaksim LitskevichChiho YoonYongkai LiYing YangYu-Xiao JiangGuangming ChengYen-Chuan LinQi ZhangZi-Jia ChengTyler A CochranDaniel MulterXian P YangBrian CasasTay-Rong ChangTitus NeupertZhujun YuanShuang JiaHsin LinNan YaoLuis BalicasFan ZhangYugui YaoM Zahid Hasan
Published in: Nature materials (2022)
Room-temperature realization of macroscopic quantum phases is one of the major pursuits in fundamental physics 1,2 . The quantum spin Hall phase 3-6 is a topological quantum phase that features a two-dimensional insulating bulk and a helical edge state. Here we use vector magnetic field and variable temperature based scanning tunnelling microscopy to provide micro-spectroscopic evidence for a room-temperature quantum spin Hall edge state on the surface of the higher-order topological insulator Bi 4 Br 4 . We find that the atomically resolved lattice exhibits a large insulating gap of over 200 meV, and an atomically sharp monolayer step edge hosts an in-gap gapless state, suggesting topological bulk-boundary correspondence. An external magnetic field can gap the edge state, consistent with the time-reversal symmetry protection inherent in the underlying band topology. We further identify the geometrical hybridization of such edge states, which not only supports the Z 2 topology of the quantum spin Hall state but also visualizes the building blocks of the higher-order topological insulator phase. Our results further encourage the exploration of high-temperature transport quantization of the putative topological phase reported here.
Keyphrases
  • room temperature
  • molecular dynamics
  • ionic liquid
  • energy transfer
  • high resolution
  • density functional theory
  • high temperature
  • monte carlo
  • quantum dots
  • single cell