Quantum ferromagnetic transition in clean Dirac metals

¹ Institute for Physical Science and Technology, University of Maryland - College Park, MD 20742, USA
² Department of Physics and Institute of Theoretical Science, University of Oregon - Eugene, OR 97403, USA
³ Materials Science Institute, University of Oregon - Eugene, OR 97403, USA

Received: 13 September 2019
Accepted: 16 September 2019

Abstract

The ferromagnetic quantum phase transition in clean metals with a negligible spin-orbit interaction is known to be first order due to a coupling of the magnetization to soft fermionic particle-hole excitations. A spin-orbit interaction gives these excitations a mass, suggesting the existence of a ferromagnetic quantum-critical point in metals with a strong spin-orbit interaction. We show that this expectation is not borne out in a large class of materials with a Dirac spectrum, since the chirality degree of freedom leads to new soft modes that again render the transition first order.