Superconducting vortex profile from fixed point measurements The Lazy Fisherman tunnelling microscopy method

TL;DR

The paper presents the 'Lazy Fisherman' STM method, which allows studying vortex profiles and dynamics in superconductors without scanning, by fixing the tip and varying the magnetic field, enabling analysis of challenging samples.

Contribution

Introduction of a novel STM technique that captures vortex behavior by fixed-tip measurements and magnetic field variation, facilitating studies on nonuniform surfaces.

Findings

Reconstructed vortex zero bias conductance profile.

Measured coherence length of 57±2 nm in MgB₂.

Enabled vortex studies in non-scannable samples.

Abstract

We introduce a mode of operation for studying the vortex phase in superconductors using scanning tunnelling microscopy (STM). While in the conventional STM method, the tip is scanned over a sample in which a fixed vortex pattern is prepared, in our "Lazy Fisherman" method the STM tip is kept fixed at a selected location while the vortices are being moved by varying the applied magnetic field. By continuously acquiring the local tunnelling conductance spectra, dI/dV(V), we detect the changes in the local density of states under the tip due to the vortex motion. With no need for scanning, the method permits one to extend the study of vortices to samples in which scanning is difficult or even impossible due to surface nonuniformity and allows one to study vortex dynamics. Using a statistical analysis of the spectra, we reconstruct the single vortex zero bias conductance profile. We apply the method to the c-axis face of an MgB$_2$ single crystal sample and obtain a vortex profile with a coherence length, xi of 57+-2 nm.