Internal pressure in superconducting Cu intercalated Bi$_2$Se$_3$

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal that internal stress from Cu intercalation enlarges the band-gap in Cu$_x$Bi$_2$Se$_3$, potentially playing a key role in its superconductivity.

Contribution

It demonstrates that internal pressure due to disorder from Cu intercalation significantly affects the electronic structure of Cu$_x$Bi$_2$Se$_3$ and may be essential for its superconducting properties.

Findings

Band-gap at $\Gamma$ point is larger in Cu$_x$Bi$_2$Se$_3$ than in pristine Bi$_2$Se$_3$

Internal stress from Cu intercalation causes the increased band-gap

Internal pressure may be necessary for superconductivity in this material

Abstract

Angle-resolved photoemission spectroscopy is used to study the band-structure of superconducting electrochemically intercalated Cu$_x$Bi$_2$Se$_3$. We find that in these samples the band-gap at the $\Gamma$ point is much larger than in pristine Bi$_2$Se$_3$. Comparison to the results of band-structure calculations indicates that the origin of this large gap is internal stress caused by disorder created by the Cu intercalation. We suggest that the internal pressure may be necessary for superconductivity in Cu$_x$Bi$_2$Se$_3$.