Hedgehog Spin-texture and Berry's Phase tuning in a Magnetic Topological Insulator

TL;DR

This paper demonstrates how magnetic doping in topological insulator films induces spin reorientation and hedgehog-like spin textures, revealing mechanisms of time-reversal symmetry breaking and control over Berry's phase, crucial for future topological magnetic applications.

Contribution

It provides experimental evidence of magnetic-induced spin textures and their modulation, advancing understanding of TR symmetry breaking in topological insulators.

Findings

Magnetically induced spin reorientation on Bi2Se3 surfaces.

Observation of hedgehog-like spin textures at low energies.

Spin texture modulation respects TR invariance despite surface gap.

Abstract

Understanding and control of spin degrees of freedom on the surfaces of topological materials are key to future applications as well as for realizing novel physics such as the axion electrodynamics associated with time-reversal (TR) symmetry breaking on the surface. We experimentally demonstrate magnetically induced spin reorientation phenomena simultaneous with a Dirac-metal to gapped-insulator transition on the surfaces of manganese-doped Bi2Se3 thin films. The resulting electronic groundstate exhibits unique hedgehog-like spin textures at low energies, which directly demonstrate the mechanics of TR symmetry breaking on the surface. We further show that an insulating gap induced by quantum tunnelling between surfaces exhibits spin texture modulation at low energies but respects TR invariance. These spin phenomena and the control of their Fermi surface geometrical phase first demonstrated in our experiments pave the way for the future realization of many predicted exotic magnetic phenomena of topological origin.