Pressure-Induced Unconventional Superconducting Phase in the Topological Insulator Bi2Se3

TL;DR

This study reveals an unconventional pressure-induced superconducting phase in Bi2Se3, with superconductivity onset above 11 GPa, and unique pressure behavior suggesting a novel pairing mechanism in topological insulators.

Contribution

It demonstrates the emergence of an unconventional superconducting phase in Bi2Se3 under high pressure, with anomalous Tc behavior and high upper critical fields indicating new pairing states.

Findings

Superconductivity appears above 11 GPa with Tc up to 7 K.

Tc remains constant despite increasing carrier concentration at high pressures.

Hc2 exceeds orbital and Pauli limits, indicating unconventional pairing.

Abstract

Simultaneous low-temperature electrical resistivity and Hall effect measurements were performed on single-crystalline Bi2Se3 under applied pressures up to 50 GPa. As a function of pressure, superconductivity is observed to onset above 11 GPa with a transition temperature Tc and upper critical field Hc2 that both increase with pressure up to 30 GPa, where they reach maximum values of 7 K and 4 T, respectively. Upon further pressure increase, Tc remains anomalously constant up to the highest achieved pressure. Conversely, the carrier concentration increases continuously with pressure, including a tenfold increase over the pressure range where Tc remains constant. Together with a quasi-linear temperature dependence of Hc2 that exceeds the orbital and Pauli limits, the anomalously stagnant pressure dependence of Tc points to an unconventional pressure-induced pairing state in Bi2Se3 that is unique among the superconducting topological insulators.