Competition between disorder and exchange splitting in superconducting ZrZn_2

TL;DR

This paper presents a simple model explaining the pressure dependence of superconductivity in ZrZn_2, emphasizing the role of exchange splitting and disorder in the suppression of T_{SC} under pressure.

Contribution

It introduces a hypothesis that the pressure dependence of T_{SC} arises from exchange splitting affecting the density of states, with implications for understanding superconductivity in ferromagnetic materials.

Findings

T_{SC} decreases with pressure until the paramagnetic state.

Disorder can suppress the minimum T_{SC} to zero.

Superconductivity's disappearance correlates with ferromagnetic transition.

Abstract

We propose a simple picture for the occurrence of superconductivity and the pressure dependence of the superconducting critical temperature, T_{SC}, in ZrZn_2. According to our hypothesis the pairing potential is independent of pressure, but the exchange splitting, E_{xc}, leads to a pressure dependence in the (spin dependent) density of states at the Fermi level, D_\sigma(\epsilon_F). Assuming p-wave pairing T_{SC} is dependent on D_\sigma(\epsilon_F) which ensures that, in the absence of non-magnetic impurities, T_{SC} decreases as pressure is applied until it reaches a minimum in the paramagnetic state. Disorder reduces this minimum to zero, this gives the illusion that the superconductivity disappears at the same pressure as ferromagnetism does.