Twofold symmetry of proximity-induced superconductivity in Bi$_{2}$Te$_{3}$/Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ heterostructures revealed by scanning tunneling microscopy

TL;DR

This study reveals twofold symmetric topological superconductivity induced by proximity effect in Bi2Te3/Bi2Sr2CaCu2O8+δ heterostructures, using scanning tunneling microscopy to analyze the superconducting gap and quasiparticle interference.

Contribution

It demonstrates the presence of twofold symmetric topological superconductivity in heterostructures combining topological insulators and high-temperature cuprate superconductors.

Findings

Superconducting gap of about 7.6 meV on 2 quintuple layer Bi2Te3 films.

Gap decreases with increasing film thickness.

Evidence of twofold symmetric superconducting gap from quasiparticle interference data.

Abstract

We observe proximity-induced superconductivity in the \textit{in situ} prepared heterostructures constructed by topological insulator Bi$_{2}$Te$_{3}$ thin films and high-temperature cuprate superconductors Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$. The superconducting gap maximum is about 7.6 meV on the surface of Bi$_{2}$Te$_{3}$ thin films with a thickness of two quintuple layers, and the gap value decreases with an increase in the film thickness. Moreover, the quasiparticle interference data show a clear evidence of a twofold symmetric superconducting gap with gap minima along one pair of the principal crystalline axes of Bi$_{2}$Te$_{3}$. This gap form is consistent with the $\Delta_{4y}$ notation of the topological superconductivity proposed in such systems. Our results provide fruitful information of the possible topological superconductivity induced by the proximity effect in high-temperature superconducting cuprates.