Quantum Coherent Transport of 1D ballistic states in second order topological insulator Bi${}_4$Br${}_4$

Abstract

We investigate quantum transport in micrometer-sized single crystals of Bi${}_4$Br${}_4$, a material predicted to be a second-order topological insulator. 1D topological states with long phase coherence times are revealed via the modulation of quantum interference with magnetic field and gate voltage. In particular, we demonstrate the existence of Aharonov-Bohm interference between 1D ballistic states several micrometers long, that we identify as phase-coherent hinge modes on neighboring step edges at the crystal surface. These Aharonov-Bohm oscillations are made possible by a disordered phase-coherent contact region, the existence of which is confirmed by scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy (STEM-EDX) of FIB lamellae. Their coherent nature modulates the transmission of the 1D edge states, leading to weak antilocalization and universal conductance fluctuations with surprisingly large characteristic fields and a strongly anisotropic behavior. These complementary experimental results provide a comprehensive, coherent description of quantum transport in Bi${}_4$Br${}_4$, and establish the material as a second-order topological insulator with topologically protected 1D ballistic states.

Main text and Supplemental material

References in corpus (21)

• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Observation of the Quantum Spin Hall Effect up to 100 Kelvin in a Monolayer Crystal
• Tunable Surface Conductivity in Bi2Se3 Revealed in Diffusive Electron Transport
• Large-Gap Quantum Spin Hall Insulator in single layer bismuth monobromide Bi${}_4$Br${}_4$
• Room-temperature quantum spin Hall edge state in a higher-order topological insulator Bi${}_4$Br${}_4$
• 2024 roadmap on 2D topological insulators
• Spin-Resolved Topology and Partial Axion Angles in Three-Dimensional Insulators
• Purely rotational symmetry-protected topological crystalline insulator $\alpha$-Bi4Br4
• Topological edge states in single- and multi-layer Bi${}_4$Br${}_4$
• Helical Liquids in Semiconductors
• Observation of the dual quantum spin Hall insulator by density-tuned correlations in a van der Waals monolayer
• 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${}_4$
• Universality of Bias- and Temperature-induced Dephasing in Ballistic Electronic Interferometers
• A robust and tunable Luttinger liquid in correlated edge of transition-metal second-order topological insulator Ta${}_2$Pd${}_3$Te${}_5$
• Facet Dependent Topological Phase Transition in Bi4Br4
• Aharonov-Bohm interference and phase-coherent surface-state transport in topological insulator rings
• Optical bulk-boundary dichotomy in a quantum spin Hall insulator
• Coalescence of multiple topological orders in quasi-one-dimensional bismuth halide chains
• Quantum transport evidence of the boundary states and Lifshitz transition in Bi${}_4$Br${}_4$
• Shear-resistant topology in quasi one-dimensional van der Waals material Bi${}_4$Br${}_4$

Cited by in corpus (1)

• Phonons Drive the Topological Phase Transition in Quasi-One-Dimensional Bi${}_4$I${}_4$