Twofold Symmetry Observed in Bi$_{2}$Te$_{3}$/FeTe Interfacial Superconductor

TL;DR

This study reveals a twofold superconducting gap symmetry in the Bi$_{2}$Te$_{3}$/FeTe interfacial superconductor using quasiparticle interference and magnetoresistance measurements, providing insights into its topological and pairing properties.

Contribution

First observation of twofold superconducting gap symmetry in Bi$_{2}$Te$_{3}$/FeTe interface using combined microscopic and macroscopic techniques.

Findings

Anisotropic superconducting gap observed via QPI patterns.

Twofold symmetry in in-plane magnetoresistance and upper critical field.

Symmetry aligns with Te-Te direction, suggesting non-magnetic origin.

Abstract

Superconducting pairing symmetry are crucial in understanding the microscopic superconducting mechanism of a superconductor. Here we report the observation of a twofold superconducting gap symmetry in an interfacial superconductor Bi$_{2}$Te$_{3}$/FeTe, by employing quasiparticle interference (QPI) technique in scanning tunneling microscopy and macroscopic magnetoresistance measurements. The QPI patterns corresponding to energies inside and outside the gap reveal a clear anisotropic superconducting gap. Furthermore, both the in-plane angle-dependent magnetoresistance and in-plane upper critical field exhibit a clear twofold symmetry. This twofold symmetry align with the Te-Te direction in FeTe, which weakens the possible generation by bi-collinear antiferromagnetism order. Our finding provides key information in further understanding of the topological properties in Bi$_{2}$Te$_{3}$/FeTe superconducting system and propels further theoretical interests in the paring mechanism in the system.