Itinerant magnetism in Weyl spin-orbit coupled Fermi gas

TL;DR

This paper investigates the effects of Weyl spin-orbit coupling on itinerant magnetism in a 3D Fermi gas, revealing the absence of ferromagnetism and the emergence of spin density waves due to spin-momentum locking.

Contribution

It introduces the novel finding that Weyl SOC suppresses ferromagnetism and promotes spin density waves at weak interactions in a 3D Fermi gas, highlighting a new mechanism for magnetic ordering.

Findings

Absence of itinerant ferromagnetism in Weyl SOC Fermi gas

Emergence of spin density waves due to spin-momentum locking

Strong SOC enables spin density waves at weak repulsion

Abstract

Magnetic ordering of itinerant fermionic systems is at the forefront of condensed matter physics dating back to Stoner's instability. Spin-orbit coupling (SOC) which couples two essential ingredients of an itinerant fermionic system, namely spin and orbital motion, opens up new horizons to this long-standing problem. Here we report that the itinerant ferromagnetism is absent in 3D Fermi gas with a Weyl SOC and various itinerant spin density waves emerge instead, which is deeply rooted in the unique symmetry and spin-momentum locking effect in spin-orbit coupled systems. What is more appealing is that, the strong SOC provides a new and efficient mechanism to realize itinerant spin density waves at extremely weak repulsion---a significant benefit for present ultra-cold atom experiment. These novel phenomena can be probed by Bragg spectroscopy, time of flight imaging and {\sl In-Situ } measurements in ultra-cold atom experiment.