Smearing of electron density of states in quasi-one-dimensional superconducting channels due to quantum phase fluctuations

Quasi-one-dimensional superconducting channels host sound-like plasma modes propagating along the sample which are associated with fluctuations of the phase of the superconducting order parameter. Interaction between these electromagnetic excitations and charge carriers affects the electron density of states (DOS). I-V characteristics of tunnel S1-I-S2 junctions, where superconducting S2 electrode is a thin nanowire in the regime of quantum fluctuations have been studied. The observed broadening of the I-V dependencies at the gap edge is interpreted as the renormalization of DOS. The results are in reasonable agreement with the model, taking into consideration plasma modes in quasi-one-dimensional superconductors.