Pyrochlore Oxide Superconductor Cd2Re2O7 Revisited

TL;DR

This paper revisits the superconducting pyrochlore oxide Cd2Re2O7, emphasizing sample quality, structural transitions, and its potential as a spin-orbit coupled metal, providing experimental insights aligned with theoretical predictions.

Contribution

It offers a comprehensive review of experimental results on Cd2Re2O7, comparing them with theoretical models of spin-orbit coupled metals to advance understanding of its unique properties.

Findings

Sample quality significantly affects superconductivity measurements.

Structural transitions involve inversion symmetry breaking at 200 K.

Experimental results support the theoretical concept of SOCM behavior in Cd2Re2O7.

Abstract

The superconducting pyrochlore oxide Cd2Re2O7 is revisited with a particular emphasis on the sample-quality issue. The compound has drawn attention as the only superconductor (Tc = 1.0 K) that has been found in the family of {\alpha}-pyrochlore oxides since its discovery in 2001. Moreover, it exhibits two characteristic structural transitions from the cubic pyrochlore structure, with the inversion symmetry broken at the first one at 200 K. Recently, it has attracted increasing attention as a candidate spin-orbit coupled metal (SOCM), in which specific Fermi liquid instability is expected to lead to an odd-parity order with spontaneous inversion-symmetry breaking [L. Fu, Phys. Rev. Lett. 115, 026401 (2015)] and parity-mixing superconductivity [V. Kozii and L. Fu: Phys. Rev. Lett. 115 (2015) 207002; Y. Wang et al., Phys. Rev. B 93 (2016) 134512]. We review our previous experimental results in comparison with those of other groups in the light of the theoretical prediction of the SOCM, which we consider meaningful and helpful for future progress in understanding this unique compound.