Quasiparticle-Self-Energy and its Effect on the Superconducting Order Parameter of the Pyrochlore Superconductor Cd2Re2O7

TL;DR

This study investigates the superconducting order parameter of Cd2Re2O7 using point contact spectroscopy, revealing strong electron-phonon interactions and quasiparticle damping effects, with potential phase transition indications below 0.8 K.

Contribution

The paper introduces a generalized theory incorporating quasiparticle self-energy into conductance spectra analysis of Cd2Re2O7, enabling precise measurement of the order parameter.

Findings

{} elta(T) increases steeply below Tc and levels off below 0.8 K.

{} Evidence of strong electron-phonon interaction.

{} Possible phase transition within the superconducting state at about 0.8 K.

Abstract

The magnitude and the temperature dependence of the superconducting order parameter {\Delta}(T) of single-crystals of Cd2Re2O7 (Tc = 1.02 K) was measured using point contact spectroscopy. In order to fit the conductance spectra and to extract the order parameter at different temperatures we generalized the Blonder-Tinkham-Klapwijk theory by including the self-energy of the quasiparticles into the Bogoliubov equations. This modification enabled excellent fits of the conductance spectra. {\Delta}(T) increases steeply below the superconducting transition temperature of 1.02 K and levels off below about 0.8 K depending on measurement directions where its value varied from 0.22(1) meV to 0.26(1) meV. Our results indicate the presence of a strong electron-phonon interaction and an enhanced quasiparticle damping and may be related to a possible phase transition within the superconducting region at about 0.8 K.