Density Waves Instability and a Skyrmion Lattice on the Surface of Strong Topological Insulators

TL;DR

This paper investigates the conditions under which spin-density waves and Skyrmion lattices form on the surface of strong topological insulators, revealing potential topologically nontrivial phases without external magnetic fields.

Contribution

It identifies the parameter regimes favoring SDW and Skyrmion lattice formation and demonstrates their topological properties in the absence of magnetic fields.

Findings

SDW states are favored at certain Fermi energies and interaction strengths.

Skyrmion lattices can form with nontrivial Chern numbers.

Surface phases can be topologically nontrivial without external magnetic fields.

Abstract

In this work we analyze the instability conditions for spin-density-waves (SDW) formation on the surface of strong topological insulators. We find that for a certain range of Fermi-energies and strength of interactions the SDW state is favored compared to the unmagnetized and the uniform-magnetization states. We also find that the SDW are of spiral nature and for a certain range of parameters a Skyrmion-lattice may form on the surface. We show that this phase may have a non trivial Chern-number even in the absence of an external magnetic field.