Topological magnetic textures in magnetic topological insulators

Nisarga Paul,Liang Fu

doi:10.1103/physrevresearch.3.033173

Abstract

The surfaces of intrinsic magnetic topological insulators (TIs) host magnetic moments exchange-coupled to Dirac electrons. We study the magnetic phases arising from tuning the electron density using variational and exact diagonalization approaches. In the dilute limit, we find that magnetic skyrmions are formed, which bind to electrons, leading to a skyrmion Wigner crystal phase while at higher densities spin spirals accompanied by chiral one-dimensional channels of electrons are formed. The binding of electrons to textures raises the possibility of manipulating textures with electrostatic gating. We determine the phase diagram capturing the competition of intrinsic spin-spin interactions and carrier density and comment on the possible application to experiments in magnetic TIs and spintronic devices such as skyrmion-based memory.

Highlights

Topological materials, topological excitations, and topological quantum effects have become a very active research frontier in condensed matter physics
Motivated by recent advances in magnetic topological insulators (TIs) and skyrmion physics, we study the magnetic phenomena arising from doping Dirac electrons
We have investigated the phases of an array of magnetic moments coupled to Dirac electrons upon tuning the electron density, motivated by intrinsic magnetic TIs subject to electrostatic gating

Summary

INTRODUCTION

Topological materials, topological excitations, and topological quantum effects have become a very active research frontier in condensed matter physics. Magnetic skyrmions have been the focus of much recent study, spurred by their observation in room-temperature materials [12,13,14], stability [15,16,17], and suitability in spintronics for next-generation memory devices [18] Both momentum-space and real-space topology can play crucial roles in magnetic topological insulators, where Dirac electrons interact with topological spin textures associated with magnetic moments [19,20,21]. Reference [20] studied the simplified case of a step-function out-of-plane skyrmion profile and found that the charged skyrmion is only energetically favorable with an external magnetic field due to particle-hole symmetry at zero field.

STRIPE PHASES

DISCUSSION