Quasiparticle damping in two-dimensional superconductors with unconventional pairing.

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 $ω^3$ 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.