Visualizing coexisting surface states in the weak and crystalline topological insulator Bi2TeI

Nurit Avraham, Abhay Kumar Nayak, Aviram Steinbok, Andrew Norris, Huixia Fu, Yan Sun, Yanpeng Qi, Lin Pan, Anna Isaeva, Alexander Zeugner, Claudia Felser, Binghai Yan, Haim Beidenkopf

Research output: Contribution to journalArticlepeer-review

Abstract

Dual topological materials are unique topological phases that host coexisting surface states of different topological nature on the same or on different material facets. Here, we show that Bi 2TeI is a dual topological insulator. It exhibits band inversions at two time reversal symmetry points of the bulk band, which classify it as a weak topological insulator with metallic states on its ‘side’ surfaces. The mirror symmetry of the crystal structure concurrently classifies it as a topological crystalline insulator. We investigated Bi 2TeI spectroscopically to show the existence of both two-dimensional Dirac surface states, which are susceptible to mirror symmetry breaking, and one-dimensional channels that reside along the step edges. Their mutual coexistence on the step edge, where both facets join, is facilitated by momentum and energy segregation. Our observation of a dual topological insulator should stimulate investigations of other dual topology classes with distinct surface manifestations coexisting at their boundaries.

Original languageEnglish
Pages (from-to)610-616
Number of pages8
JournalNature Materials
Volume19
Issue number6
Early online date23 Mar 2020
DOIs
StatePublished - 1 Jun 2020

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