Robust, switchable, C-related, Superconducting Nanostructure at the Apex of a W tip

TL;DR

This paper presents a method to create a switchable, superconducting tungsten tip at the apex of an STM, enabling atomic resolution and stable superconductivity up to 3.3 K and magnetic fields above 3T, with implications for graphene studies.

Contribution

A novel in-situ fabrication technique for superconducting tungsten tips at the STM apex, with controllable switching and high stability.

Findings

Superconducting transition temperature of 3.3 K.

Critical magnetic field exceeds 3 Tesla.

Robustness and atomic resolution capability of the superconducting tip.

Abstract

We report on a controlled method to fabricate in-situ a superconducting (SC) nanostructure at the apex of the standard W tip of a Scanning Tunnelling Microscope (STM) by pulsing the tunnelling voltage on a graphene covered metal surface. We have characterized the SC properties of the resulting tip as a function of temperature and magnetic field, obtaining a transition temperature of 3.3 K and a critical field well above 3T. The SC nanotip is robust, stable, and achieves atomic resolution. The non-SC tip can be easily recovered by controlled voltage pulsing on a clean metal surface. The present result should be taken into account when studying zero-bias features like Kondo resonances or superconductivity on graphene-based systems by means of STM using tungsten tips.