Pressure-induced superconductivity and topological phase transitions in the topological nodal-line semimetal SrAs3

TL;DR

This study explores pressure-induced phase transitions in SrAs3, revealing superconductivity and topological changes, suggesting it as a candidate for topological superconductor with potential surface state superconductivity.

Contribution

The paper reports the discovery of superconductivity and topological phase transitions in SrAs3 under high pressure, combining experimental and theoretical insights.

Findings

Lifshitz transition below 1 GPa

Superconductivity above 20 GPa

Emergence of topological crystalline insulator state

Abstract

Topological nodal-line semimetals (TNLSMs) are materials whose conduction and valence bands cross each other, meeting a topologically-protected closed loop rather than discrete points in the Brillouin zone (BZ). The anticipated properties for TNLSMs include drumhead-like nearly flat surface states, unique Landau energy levels, special collective modes, long-range Coulomb interactions, or the possibility of realizing high-temperature superconductivity. Recently, SrAs3 has been theoretically proposed and then experimentally confirmed to be a TNLSM. Here, we report high-pressure experiments on SrAs3, identifying a Lifshitz transition below 1 GPa and a superconducting transition accompanied by a structural phase transition above 20 GPa. A topological crystalline insulator (TCI) state is revealed by means of density functional theory (DFT) calculations on the emergent high-pressure phase. As the counterpart of topological insulators, TCIs possess metallic boundary states protected by crystal symmetry, rather than time reversal. In consideration of topological surface states (TSSs) and helical spin texture observed in the high-pressure state of SrAs3, the superconducting state may be induced in the surface states, and is most likely topologically nontrivial, making pressurized SrAs3 a strong candidate for topological superconductor.