Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 28: Topological Insulators (joint session MA/HL)

HL 28.4: Vortrag

Dienstag, 18. März 2025, 14:45–15:00, H16

Local and Global Topological Characteristics of Local Magnetic Moments Coupled to Chern Insulators — •Devesh Vaish and Michael Potthoff — I. Institute of Theoretical Physics, Department of Physics, University of Hamburg

A magnetic impurity, modelled as a classical spin and locally exchange coupled to a Chern insulator may cause in-gap bound states. Their nature can be very different depending on the (k-space) topological phase of the Chern insulator. Here we study several impurity spins coupled to a QWZ model and analyze, for different k-space topological phases, the additional "local" topological properties on the manifold of impurity-spin configurations (S-space). In case of R>1 spins, the R-th spin-Chern number serves as a topological invariant on S-space. Varying the local exchange-coupling strength, we find local topological phase transitions and relate them to Fermi-energy crossings of in-gap states. In addition, we compute the first spin-Chern number for various physically motivated closed two-dimensional sub-manifolds of the full configuration space and relate those to the R-th spin-Chern number.

Keywords: Chern insulator; bound states; magnetic impurities; local topological transition