Colossal anisotropy in diluted magnetic topological insulators

TL;DR

This paper investigates how dilute magnetic doping affects the surface states of a 3D topological insulator, revealing colossal magnetic anisotropy and circulating electronic currents due to exchange interactions.

Contribution

It uncovers a large magnetic anisotropy energy and persistent currents induced by magnetic doping on topological insulator surfaces, highlighting novel magnetic and electronic phenomena.

Findings

Colossal magnetic anisotropy energy comparable to critical temperature.

Persistent circulating electronic currents around magnetic atoms and edges.

Strong exchange coupling effects on surface Dirac electrons.

Abstract

We consider dilute magnetic doping in the surface of a three dimensional topological insulator where a two dimensional Dirac electron gas resides. We find that exchange coupling between magnetic atoms and the Dirac electrons has a strong and peculiar effect on both. First, the exchange-induced single ion magnetic anisotropy is very large and favors off-plane orientation. In the case of ferromagnetically ordered phase we find a colossal magnetic anisotropy energy, of the order of the critical temperature. Second, a persistent electronic current circulates around the magnetic atom and, in the case of a ferromagnetic phase, around the edges of the surface.