Interfacial superconductivity and zero bias peak in quasi-one-dimensional Bi2Te3/Fe1+yTe heterostructure nanostructures

TL;DR

This study demonstrates that interfacial superconductivity persists in one-dimensional Bi2Te3/Fe1+yTe heterostructures, revealing enhanced fluctuation effects and a zero-bias conductance peak suggestive of topological superconductivity and Andreev bound states.

Contribution

The paper introduces a top-down fabrication method for 1D Bi2Te3/Fe1+yTe nanostructures that retain interfacial superconductivity, highlighting the potential for topological superconductivity in reduced dimensions.

Findings

Superconductivity is preserved in nanowires of ~100 nm width.

Differential conductance shows a twin-gap structure similar to 2D heterostructures.

Zero-bias conductance peak suggests topological Andreev bound states.

Abstract

Bi2Te3/Fe1+yTe heterostructures are known to exhibit interfacial superconductivity between two non-superconducting materials: Fe1+yTe as the parent compound of Fe-based superconducting materials and the topological insulator Bi2Te3. Here, we present a top-down approach starting from two-dimensional (2D) heterostructures to fabricate one-dimensional (1D) Bi2Te3/Fe1+yTe nanowires or narrow nanoribbons. We demonstrate that the Bi2Te3/Fe1+yTe heterostructure remains intact in nanostructures of widths on the order of 100 nm and the interfacial superconductivity is preserved, as evidenced by electrical transport and Andreev reflection point contact spectroscopy experiments measured at the end of the nanowire. The differential conductance shows a similar superconducting twin-gap structure as in two-dimensional heterostructures, but with enhanced fluctuation effects due to the lower dimensionality. A zero-bias conductance peak indicates the presence of an Andreev bound state and given the involvement of the topological Bi2Te3 surface state, we discuss a possible topological nature of superconductivity with strong interplay with an emerging ferromagnetism due to the interstitial excess iron in the Fe1+yTe layer, developing in parallel with superconductivity at low temperatures.