Purely rotational symmetry-protected topological crystalline insulator $\alpha$-Bi4Br4

Abstract

Recent theoretical advances have proposed a new class of topological crystalline insulator (TCI) phases protected by rotational symmetries. Distinct from topological insulators (TIs), rotational symmetry-protected TCIs are expected to show unique topologically protected boundary modes: First, the surface normal to the rotational axis features unpinned Dirac surface states whose Dirac points are located at generic k points. Second, due to the higher-order bulk boundary correspondence, a 3D TCI also supports 1D helical edge states. Despite the unique topological electronic properties, to date, purely rotational symmetry-protected TCIs remain elusive in real materials. Using first-principles band calculations and theoretical modeling, we identify the van der Waals material $\alpha$-Bi4Br4 as a TCI purely protected by rotation symmetry. We show that the Bi4Br4's (010) surface exhibits a pair of unpinned topological Dirac fermions protected by the two-fold rotational axis. These unpinned Dirac fermions show an exotic spin texture highly favorable for spin transport and a band structure consisting of van Hove singularities due to Lifshitz transition. We also identify 1D topological hinge states along the edges of an $\alpha$-Bi4Br4 rod. We further discuss how the proposed topological electronic properties in $\alpha$-Bi4Br4 can be observed by various experimental techniques.

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Cited by in corpus (22)

• All Topological Bands of All Nonmagnetic Stoichiometric Materials
• Topological Materials Discovery from Crystal Symmetry
• Room-temperature quantum spin Hall edge state in a higher-order topological insulator Bi${}_4$Br${}_4$
• Spin-Resolved Topology and Partial Axion Angles in Three-Dimensional Insulators
• A Higher-Order Topological Insulator Phase in a Modulated Haldane Model
• Topological electronic structure and spin texture of quasi-one-dimensional higher-order topological insulator Bi4Br4
• Transport response of topological hinge modes in $\alpha$-Bi${}_4$Br${}_4$
• Generation of higher-order topological insulators using periodic driving
• Facet Dependent Topological Phase Transition in Bi4Br4
• Topological crystalline insulator state with type-II Dirac fermions in transition metal dipnictides
• Optical bulk-boundary dichotomy in a quantum spin Hall insulator
• Quantum transport evidence of the boundary states and Lifshitz transition in Bi${}_4$Br${}_4$
• A robust weak topological insulator in a bismuth halide Bi4Br2I2
• Mass Acquisition of Dirac Fermions in Bi4I4 by Spontaneous Symmetry Breaking
• Discovery of Ĉ${}_2$ rotation anomaly in topological crystalline insulator SrPb
• Computing the ${\mathbb{Z}}_2$ Invariant in Two-Dimensional Strongly-Correlated Systems
• Electronic structure in a transition metal dipnictide TaAs2
• Signature of quantum phase transition manifested in quantum fidelity at finite temperature
• RKKY interaction in helical higher-order topological insulators
• Interacting Crystalline Topological Insulators in two-dimensions with Time-Reversal Symmetry
• Quantum Coherent Transport of 1D ballistic states in second order topological insulator Bi${}_4$Br${}_4$
• Probing the topological protection of edge states in multilayer tungsten ditelluride with the superconducting proximity effect