Topological insulator ring with magnetic impurities

Abstract

Topological insulators exhibit gapless edge or surface states that are topologically protected by time-reversal symmetry. However, several promising candidates for topologically insulating materials (such as Bi${}_2$Se${}_3$ and HgTe) contain spinful nuclei or other types of magnetic impurities that break time-reversal symmetry. We investigate the consequences of such impurities coupled to electronic edge states in a topological insulator quantum ring threaded by a magnetic flux. We use spin conservation and additional symmetry arguments to derive a universal formula for the spectrum of propagating edge modes in terms of the amplitude of transmission through the impurity. Our results apply for impurities of arbitrary spin. We show that there exists an energy regime in which the spectrum becomes nearly independent of the flux and significant spectral gaps form. We further analyze the electron-impurity entanglement entropy, finding that maximal entanglement occurs near the gaps in the spectrum. Our predictions can be investigated with quantum ring transport interference experiments or through spin-resolved STM measurements, providing a new approach to understand the role of impurities in topological insulator edge transport.

15 pages, 9 figures

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Cited by in corpus (8)

• Transport tuning of photonic topological edge states by optical cavities
• Helical Liquids in Semiconductors
• Optical response of a topological-insulator--quantum-dot hybrid interacting with a probe electric field
• Robustness of Helical Edge States Under Edge Reconstruction
• Dynamic Nuclear Polarization from Topological Insulator Helical Edge States
• Dynamic impurities in two-dimensional topological insulator-edge states
• Scanning Tunneling Microscopy Study of Epitaxial Fe3GeTe2 Monolayers on Bi2Te3
• Edge Reconstruction in a Quantum Spin Hall Insulator