Discontinuous Transition to Superconducting Phase

TL;DR

This paper investigates how the presence of odd-frequency Cooper pairs causes a discontinuous transition to superconductivity, driven by their paramagnetic response, especially at finite temperatures.

Contribution

It reveals that odd-frequency pairing correlations lead to a discontinuous superconducting transition, a novel insight into the phase transition behavior in such systems.

Findings

Discontinuous transition occurs when odd-frequency correlations are large.

Paramagnetic response of odd-frequency pairs drives the instability.

Transition temperature features a sudden change in pair potential.

Abstract

We discuss the instability of uniform superconducting states that contain the pairing correlations belonging to the odd-frequency symmetry class. The instability originates from the paramagnetic response of odd-frequency Cooper pairs and is considerable at finite temperatures. As a result, the pair potential varies discontinuously at the transition temperature when the amplitude of the odd-frequency pairing correlation functions is sufficiently large. The discontinuous transition to the superconducting phase is a general feature of superconductors that include odd-frequency Cooper pairs.