On the use of STM superconducting tips at very low temperatures

TL;DR

This paper demonstrates high-resolution tunneling spectroscopy using superconducting tips at very low temperatures, exploring Josephson effects and magnetic field applications with atomic-scale resolution.

Contribution

It introduces the use of in-situ fabricated superconducting tips for high-resolution spectroscopy and discusses the potential for atomic-scale scanning Josephson spectroscopy.

Findings

Spectroscopic resolution of 15 microeV achieved.

Observation of Josephson current with Pb and Al tips.

Feasibility of atomic-scale scanning Josephson spectroscopy discussed.

Abstract

We report on high quality local tunnel spectroscopy measurements in superconductors using in-situ fabricated superconducting tips as counterelectrode. The experiments were made at very low temperatures using a dilution refrigerator and a 3He cryostat. Spectra obtained with superconducting tip and sample of Al show that the spectroscopic resolution of our set-up is of 15 microeV . Following the observation of Josephson current in tunneling regime (with tips of Pb and of Al), we discuss the feasibility of Scanning Josephson Spectroscopy with atomic size resolution. Experiments showing new applications of these superconducting tips under applied external magnetic fields are also reported.