Anomalous Cooper pair interference on Bi2Te3 surface

TL;DR

This study uses phase-sensitive measurements on Bi2Te3-based superconducting devices to reveal anomalous Cooper pair interference patterns, indicating p_x+ip_y-like superconductivity on the surface, which is significant for topological quantum research.

Contribution

It provides experimental evidence of anomalous Cooper pair interference on Bi2Te3 surfaces, suggesting p-wave-like superconductivity with a 2π Berry phase, advancing understanding of topological superconductivity.

Findings

Identified two types of Cooper interference patterns, one s-wave like and one anomalous.

Discovered a phase shift in surface state interference, indicating p_x+ip_y-like pairing.

Supported the presence of a 2π Berry phase in surface Cooper pairs.

Abstract

It is believed that the edges of a chiral p-wave superconductor host Majorana modes, relating to a mysterious type of fermions predicted seven decades ago. Much attention has been paid to search for p-wave superconductivity in solid-state systems, including recently those with strong spin-orbit coupling (SOC). However, smoking-gun experiments are still awaited. In this work, we have performed phase-sensitive measurements on particularly designed superconducting quantum interference devices constructing on the surface of topological insulators Bi2Te3, in such a way that a substantial portion of the interference loop is built on the proximity-effect-induced superconducting surface. Two types of Cooper interference patterns have been recognized at low temperatures. One is s-wave like and is contributed by a zero-phase loop inhabited in the bulk of Bi2Te3. The other, being identified to relate to the surface states, is anomalous for that there is a phase shift between the positive and negative bias current directions. The results support that the Cooper pairs on the surface of Bi2Te3 have a 2\pi Berry phase which makes the superconductivity p_x+ip_y-wave-like. Mesoscopic hybrid rings as constructed in this experiment are presumably arbitrary-phase loops good for studying topological quantum phenomena.