title: Mirror-symmetry protected non-TRIM surface state in the weak topological insulator Bi2TeI.
abstract: Strong topological insulators (TIs) support topological surfaces states on any crystal surface. In contrast, a weak, time-reversal-symmetry-driven TI with at least one non-zero v1, v2, v3 ℤ2 index should host spin-locked topological surface states on the surfaces that are not parallel to the crystal plane with Miller indices (v1 v2 v3). On the other hand, mirror symmetry can protect an even number of topological states on the surfaces that are perpendicular to a mirror plane. Various symmetries in a bulk material with a band inversion can independently preordain distinct crystal planes for realization of topological states. Here we demonstrate the first instance of coexistence of both phenomena in the weak 3D TI Bi2TeI which (v1 v2 v3) surface hosts a gapless spin-split surface state protected by the crystal mirror-symmetry. The observed topological state has an even number of crossing points in (r-M)the directions of the 2D Brillouin zone due to a non-TRIM bulk-band inversion. Our findings shed light on hitherto uncharted features of the electronic structure of weak topological insulators and open up new vistas for applications of these materials in spintronics.
authors: Tomsk State University, pr. Lenina, 36, Tomsk, 634050 Russia.|St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg, 199034 Russia.
authors: I P
authors: IP
authors: Rusinov
authors: Tomsk State University, pr. Lenina, 36, Tomsk, 634050 Russia.
authors: T V
authors: TV
authors: Menshchikova
authors: Technische Universität Dresden, Bergstraße, 66, Dresden, D-01069, Germany.
authors: A
authors: A
authors: Isaeva
authors: Tomsk State University, pr. Lenina, 36, Tomsk, 634050 Russia.|St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg, 199034 Russia.|Institute of Strength Physics and Materials Science, pr. Akademicheskiy, 2/4, Tomsk, 634021 Russia.
authors: S V
authors: SV
authors: Eremeev
authors: Tomsk State University, pr. Lenina, 36, Tomsk, 634050 Russia.|Institute of Strength Physics and Materials Science, pr. Akademicheskiy, 2/4, Tomsk, 634021 Russia.
authors: Yu M
authors: YM
authors: Koroteev
authors: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal, 4, 20018 San Sebastián/Donostia, Basque Country, Spain.
authors: M G
authors: MG
authors: Vergniory
authors: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal, 4, 20018 San Sebastián/Donostia, Basque Country, Spain.|Departamento de Física de Materiales, Facultad de Ciencias Químicas, UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain.|Centro de Física de Materiales CFM-MPC, Centro Mixto CSIC-UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain.
authors: P M
authors: PM
authors: Echenique
authors: Tomsk State University, pr. Lenina, 36, Tomsk, 634050 Russia.|St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg, 199034 Russia.|Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal, 4, 20018 San Sebastián/Donostia, Basque Country, Spain.|Departamento de Física de Materiales, Facultad de Ciencias Químicas, UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain.|Centro de Física de Materiales CFM-MPC, Centro Mixto CSIC-UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain.
authors: E V
authors: EV
authors: Chulkov