Interface-Enhanced Superconductivity in Ultrathin TiN Proximitized by Topological Insulators

TL;DR

This study demonstrates interface-enhanced superconductivity in ultrathin TiN topological insulator heterostructures, revealing a novel mechanism for manipulating superconductivity through interface engineering and charge transfer effects.

Contribution

It introduces a new approach to enhance superconductivity in TI-TiN heterostructures via interface charge transfer and detailed first-principles analysis.

Findings

Observation of Tc enhancement in TiN due to interface effects

Band structure shift correlates with Tc increase

Interfacial charge transfer explains superconductivity enhancement

Abstract

High-quality topological insulator-superconductor (TI-SC) heterostructure with an atomically sharp and well-controlled interface is crucial for realizing topological superconductivity and topological quantum qubit. In particular, many studies of TI-SC heterostructures have focused on inducing superconducting gap in the TI layer via proximity effect, while the active manipulation of superconductivity in the SC layer remains largely unexplored. In this work, we fabricated TI/TiN heterostructures using highly air-stable, ultrathin TiN films as the SC layer, and observed an interface-enhanced superconductivity that contrasts with the conventional proximity effect in superconductor-normal metal interface. Band structure measurements reveal a consistent shift of Dirac point with Tc enhancement. Interfacial charge transfer provides a plausible explanation for this shift based on the systematic analysis and is therefore a likely contributor to the observed Tc enhancement. First principles calculations elucidate the charge transfer pathways, highlighting the critical role of the interfacial BiTe (BiSe)bilayer. Our results not only provide a tunable TI-SC hybrid system with robust superconductivity at ultrathin thickness, but also offer a potential route for manipulating superconductivity in TI-SC heterostructures via interface engineering.