Scanning Tunneling Microscopy in the superconductor LaSb2

TL;DR

This study uses low-temperature scanning tunneling microscopy to investigate the layered superconductor LaSb2, revealing a superconducting gap consistent with BCS theory but with broadening and high Fermi level states.

Contribution

First detailed STM/STS analysis of LaSb2 at 0.15 K showing superconducting gap and surface atomic patterns.

Findings

Superconducting gap of 0.17 meV observed

T_c determined to be 1.2 K from conductance measurements

High density of states at Fermi level with broad spectral features

Abstract

We present very low temperature (0.15 K) scanning tunneling microscopy and spectroscopy experiments in the layered superconductor LaSb$_2$. We obtain topographic microscopy images with surfaces showing hexagonal and square atomic size patterns, and observe in the tunneling conductance a superconducting gap. We find well defined quasiparticle peaks located at a bias voltage comparable to the weak coupling s-wave BCS expected gap value (0.17 meV). The amount of states at the Fermi level is however large and the curves are significantly broadened. We find T$_c$ of 1.2 K by following the tunneling conductance with temperature.