Quantum fluctuation driven first order phase transition in weak ferromagnetic metals

TL;DR

This paper demonstrates that quantum fluctuations induce a line of weak first order phase transitions between ferromagnetic and paramagnetic phases in local Fermi liquids, predicting a quantum triple point where these phases and superconductivity meet.

Contribution

It reveals a quantum fluctuation-driven mechanism for first order phase transitions and introduces the concept of a quantum triple point in ferromagnetic metals.

Findings

Quantum fluctuations cause weak first order transitions.

Superconductivity is only possible in the ferromagnetic phase.

A quantum triple point exists where three phases meet at T=0.

Abstract

In a local Fermi liquid (LFL), we show that there is a line of weak first order phase transitions between the ferromagnetic and paramagnetic phases due to purely quantum fluctuations. We predict that an instability towards superconductivity is only possible in the ferromagnetic state. At T=0 we find a point on the phase diagram where all three phases meet and we call this a quantum triple point (QTP). A simple application of the Gibbs phase rule shows that only these three phases can meet at the QTP. This provides a natural explanation of the absence of superconductivity at this point coming from the paramagnetic side of the phase diagram, as observed in the recently discovered ferromagnetic superconductor, $UGe_{2}$.