The pressure-enhanced superconducting phase of Sr$_x$-Bi$_2$Se$_3$ probed by hard point contact spectroscopy

TL;DR

This study uses point contact spectroscopy to investigate the pressure-induced superconducting phase of Sr-intercalated Bi2Se3, revealing signs of unconventional superconductivity and providing insights into its spectroscopic properties.

Contribution

It demonstrates that the high-pressure superconducting phase can be accessed via mesoscopic point contact, enabling spectroscopic analysis of its unconventional nature.

Findings

High-pressure phase shows enhanced T_c (~2.9 K)

Point contact spectroscopy indicates unconventional superconductivity

Magnetic field response supports non-traditional pairing mechanisms

Abstract

The superconducting systems emerging from topological insulators upon metal ion intercalation or application of high pressure are ideal for investigation of possible topological superconductivity. In this context, Sr-intercalated Bi$_2$Se$_3$ is specially interesting because it displays pressure induced re-entrant superconductivity where the high pressure phase shows almost two times higher $T_c$ than the ambient superconducting phase ( $T_C\sim$ 2.9 K). Interestingly, unlike the ambient phase, the pressure-induced superconducting phase shows strong indication of unconventional superconductivity. However, since the pressure-induced phase remains inaccessible to spectroscopic techniques, the detailed study of the phase remained an unattained goal. Here we show that the high-pressure phase can be realized under a mesoscopic point contact, where transport spectroscopy can be used to probe the spectroscopic properties of the pressure-induced phase. We find that the point contact junctions on the high-pressure phase show unusual response to magnetic field supporting the possibility of unconventional superconductivity.