Superconducting properties of Cu intercalated Bi$_2$Se$_3$ studied by Muon Spin Spectroscopy

TL;DR

This study uses muon spin rotation to investigate the superconducting properties of Cu-intercalated Bi$_2$Se$_3$, revealing a transition below 4 K and a large London penetration depth consistent with BCS theory.

Contribution

First muon spin rotation measurements on Cu-intercalated Bi$_2$Se$_3$, providing insights into its superconducting gap symmetry and magnetic field distribution.

Findings

Superconducting transition observed below 4 K.

Large London penetration depth (~1.6 μm) in the ab plane.

Temperature dependence of magnetic broadening follows BCS prediction.

Abstract

We present muon spin rotation measurements on superconducting Cu intercalated Bi$_2$Se$_3$, which was suggested as a realization of a topological superconductor. We observe a clear evidence of the superconducting transition below 4 K, where the width of magnetic field distribution increases as the temperature is decreased. The measured broadening at mK temperatures suggests a large London penetration depth in the $ab$ plane ($\lambda_{\mathrm{eff}}\sim 1.6$ $\mathrm{\mu}$m). We show that the temperature dependence of this broadening follows the BCS prediction, but could be consistent with several gap symmetries.