Emergent Interfacial Superconductivity between Twisted Cuprate Superconductors

TL;DR

This paper demonstrates that twisted interfaces between cuprate superconductors can host emergent interfacial superconductivity with twist-angle-dependent Josephson effects, revealing potential pathways toward high-temperature topological superconductivity.

Contribution

The study introduces a novel cryogenic assembly method to fabricate atomically sharp twisted cuprate interfaces and investigates their twist-angle-dependent superconducting properties.

Findings

Josephson critical current density varies with twist angle, peaking at small angles.

Superconducting coherence persists near 45 degrees due to co-tunneling of Cooper pairs.

Evidence suggests potential for high-temperature topological superconductivity.

Abstract

Twisted interfaces between stacked van der Waals cuprate crystals enable tunable Josephson coupling between in-plane anisotropic superconducting order parameters. Employing a novel cryogenic assembly technique, we fabricate Josephson junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. The Josephson critical current density sensitively depends on the twist angle, reaching the maximum value comparable to that of the intrinsic junctions at small twisting angles, and is suppressed by almost 2 orders of magnitude yet remains finite close to 45 degree twist angle. Through the observation of fractional Shapiro steps and the analysis of Fraunhofer patterns we show that the remaining superconducting coherence near 45 degree is due to the co-tunneling of Cooper pairs, a necessary ingredient for high-temperature topological superconductivity.