Fluctuation-induced pair density wave in itinerant ferromagnets

TL;DR

This paper develops a unified quantum order-by-disorder framework to show how magnetic fluctuations near quantum criticality can induce a novel pair density wave phase in itinerant ferromagnets.

Contribution

It introduces a general theoretical approach that unifies the understanding of magnetic and superconducting instabilities and predicts a new intertwined phase, the pair density wave.

Findings

Magnetic fluctuations can induce a pair density wave phase.

Unified framework describes both superconducting and magnetic instabilities.

Intertwining of instabilities leads to novel phase formation.

Abstract

Magnetic fluctuations near to quantum criticality can have profound effects. They lead to characteristic scaling at high temperature which may ultimately give way to a reconstruction of the phase diagram and the formation of new phases at low temperatures. The ferromagnet UGe2 is unstable to p-wave superconducting order -- an effect presaged by the superfluidity in He3 -- whereas in CeFePO fluctuations drive the formation of spiral magnetic order. Here we develop a general quantum order-by-disorder description of these systems that encompasses both of these instabilities within a unified framework. This allows us to demonstrate that in fact these instabilities intertwine to form a new phase, a pair density wave.