Anomalous suppression of the superfluid density in the CuxBi2Se3 superconductor upon progressive Cu intercalation

TL;DR

This study investigates how progressive Cu intercalation introduces disorder in CuxBi2Se3, leading to an unexpected suppression of superfluid density while only moderately reducing the critical temperature, supporting odd-parity pairing.

Contribution

It provides experimental evidence of disorder effects on superfluid density in CuxBi2Se3, highlighting anomalous suppression linked to potential odd-parity pairing in topological superconductors.

Findings

Superfluid density is significantly suppressed by Cu intercalation.

Transition temperature T_c is only moderately affected.

Results support the odd-parity pairing hypothesis.

Abstract

CuxBi2Se3 was recently found to be likely the first example of a time-reversal-invariant topological superconductor accompanied by helical Majorana fermions on the surface. Here we present that progressive Cu intercalation into this system introduces significant disorder and leads to an anomalous suppression of the superfluid density which was obtained from the measurements of the lower critical field. At the same time, the transition temperature T_c is only moderately suppressed, which agrees with a recent prediction for the impurity effect in this class of topological superconductors bearing strong spin-orbit coupling. Those unusual disorder effects give support to the possible odd-parity pairing state in CuxBi2Se3.