Quasiparticle damping in two-dimensional superconductors with unconventional pairing.

TL;DR

This paper investigates how quasiparticle excitations in two-dimensional unconventional superconductors are damped, revealing a gapless $$ behavior at low frequencies and analyzing the crossover to normal-state regimes with frequency and temperature.

Contribution

It provides a detailed calculation of quasiparticle damping in 2D superconductors with nodes, including explicit models and the effects of spectrum parametrization.

Findings

At zero temperature, damping shows gapless  behavior at nodal points.

Damping transitions to normal-state behavior at higher frequencies.

Damping depends on the spectrum details, with explicit models analyzed.

Abstract

We calculate the damping of excitations due to four-fermionic interaction in the case of two-dimensional superconductor with nodes in the spectrum. At zero temperature and low frequencies it reveals gapless $\omega^3$ behavior at the nodal points. With the frequency increasing the crossover to the normal-state regimes appears. At high frequencies the damping strongly depends on details of a normal-state spectrum parametrization. Two important particular cases such as the models of almost free and tight-binding electrons are studied explicitly and the characteristic scales are expressed through the model-free parameters of the spectrum at the nodal points. The possibility of crossover in temperature dependence of damping in the superconducting phase is discussed.