Hybridization and superconducting gaps in heavy-fermion superconductor PuCoGa5 probed via the dynamics of photoinduced quasiparticles

TL;DR

This study investigates quasiparticle relaxation in PuCoGa5, revealing a hybridization gap and suggesting non-phononic pairing mechanisms in this heavy-fermion superconductor.

Contribution

It provides experimental evidence of a hybridization gap and challenges phonon-mediated pairing in PuCoGa5 through ultrafast spectroscopy.

Findings

Quasiparticle relaxation time increases at low temperatures

Presence of a hybridization gap in the electronic density of states

Modification of reflectance consistent with heavy quasiparticles

Abstract

We have examined the relaxation of photoinduced quasiparticles in the heavy-fermion superconductor PuCoGa5. The deduced electron-phonon coupling constant is incompatible with the measured superconducting transition temperature Tc=18.5 K, which speaks against phonon-mediated superconducting pairing. Upon lowering the temperature, we observe an order-of-magnitude increase of the quasiparticle relaxation time in agreement with the phonon bottleneck scenario - evidence for the presence of a hybridization gap in the electronic density of states. The modification of photoinduced reflectance in the superconducting state is consistent with the heavy character of the quasiparticles that participate in Cooper pairing.