Topological electronic structure and spin texture of quasi-one-dimensional higher-order topological insulator Bi4Br4

Abstract

The notion of topological insulators (TIs), characterized by an insulating bulk and conducting topological surface states, can be extended to higher-order topological insulators (HOTIs) hosting gapless modes localized at the boundaries of two or more dimensions lower than the insulating bulk1-5. In this work, by performing high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements with submicron spatial and spin resolutions, we systematically investigate the electronic structure and spin texture of quasi-one-dimensional (1D) HOTI candidate Bi4Br4. In contrast to the bulk-state-dominant spectra on the (001) surface, we observe gapped surface states on the (100) surface, whose dispersion and spin-polarization agree well with our ab initio calculations. Moreover, we reveal in-gap states connecting the surface valence and conduction bands, which is an explicit signature of the existence of hinge states inside the (100) surface gap. Our findings provide compelling evidence for the HOTI phase of Bi4Br4. The identification of the higher-order topological phase will lay the promising prospect of applications based on 1D spin-momentum locked current in electronic and spintronic devices.

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Cited by in corpus (10)

• Spin-Resolved Topology and Partial Axion Angles in Three-Dimensional Insulators
• Coalescence of multiple topological orders in quasi-one-dimensional bismuth halide chains
• Topological Phase Transition in Quasi-One-Dimensional Bismuth Iodide Bi4I4
• Mass Acquisition of Dirac Fermions in Bi4I4 by Spontaneous Symmetry Breaking
• Shear-resistant topology in quasi one-dimensional van der Waals material Bi${}_4$Br${}_4$
• Quantum Coherent Transport of 1D ballistic states in second order topological insulator Bi${}_4$Br${}_4$
• Unveiling Topological Hinge States in the Higher-Order Topological Insulator WTe${}_2$ Based on the Fractional Josephson Effect
• Majorana vortex phases in time-reversal invariant higher-order topological insulators and topologically trivial insulators
• Phonons Drive the Topological Phase Transition in Quasi-One-Dimensional Bi${}_4$I${}_4$
• Breakdown of the symmetry constraint in a Floquet topological insulator