Chirality reversal at finite magnetic impurity strength and local signatures of a topological phase transition

Abstract

We study the honeycomb lattice with a single magnetic impurity modeled by adding imaginary next-nearest-neighbor hopping ih on a single hexagon. This Haldane defect gives a topological mass term to the gapless Dirac cones and generates chirality. For a small density of defects Neehus et al [arXiv:2405.19289] found that the system's chirality reverses at a critical hc ~ 0.95 associated with an unexpected tri-critical point of Dirac fermions at zero defect density. We investigate this zero-density limit by analyzing a single defect and computing two experimentally relevant measures of chirality: (1) orbital magnetization via local Chern marker, a bulk probe of all occupied states; and (2) electronic currents of low-energy states. Both probes show a chirality reversal at a critical hc ~ 0.9--1. Motivated by this consistency we propose a defect-scale toy model whose low energy states reverse their chirality at hc' ~ 0.87. Remarkably, the same pair of zero energy bound states also generate the critical point hc in the full impurity projected T-matrix. Our results show how the chirality reversal produced by an impurity can be observed either in local probes or in the global topology and suggest a possible role of the microscopic defect structure at the critical point.

10 pages, 5 figures; appendix 4 pages, 5 figures. v2: Published version

References in corpus (13)

• Magnetism in Graphene Induced by Single-Atom Defects
• Topological Anderson Insulator
• Vanishing edge currents in non-$p$-wave topological chiral superconductors
• Patched Green's function techniques for two dimensional systems: Electronic behaviour of bubbles and perforations in graphene
• In-gap impurity states as the hallmark of the Quantum Spin Hall phase
• Local Chern Marker for Periodic Systems
• Local control of a single nitrogen-vacancy center by nanoscale engineered magnetic domain wall motions
• Impurity induced current in a Chern insulator
• Bound states and local topological phase diagram of classical impurity spins coupled to a Chern insulator
• Magnetic order through Kondo coupling to quantum spin liquids
• Disorder-induced currents as signatures of chiral superconductivity
• Genuine topological Anderson insulator from impurity induced chirality reversal
• Sharp spectroscopic fingerprints of disorder in an incompressible magnetic state