Gapped surface states in a strong-topological-insulator material

A. P. Weber, Q. D. Gibson, Huiwen Ji, A. N. Caruso, A. V. Fedorov, R. J. Cava, T. Valla

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24 Scopus citations


A three-dimensional strong-topological insulator or semimetal hosts topological surface states which are often said to be gapless so long as time-reversal symmetry is preserved. This narrative can be mistaken when surface state degeneracies occur away from time-reversal-invariant momenta. The mirror invariance of the system then becomes essential in protecting the existence of a surface Fermi surface. Here we show that such a case exists in the strong-topological-semimetal Bi4Se3. Angle-resolved photoemission spectroscopy and ab initio calculations reveal partial gapping of surface bands on the Bi2Se3 termination of Bi4Se3(111), where an 85 meV gap along Γ¯K¯ closes to zero toward the mirror-invariant Γ¯M¯ azimuth. The gap opening is attributed to an interband spin-orbit interaction that mixes states of opposite spin helicity.

Original languageEnglish (US)
Article number256401
JournalPhysical review letters
Issue number25
StatePublished - Jun 23 2015

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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