Scanning tunneling spectroscopy of layers of superconducting 2H-TaSe$_\textbf{2}$: Evidence for a zero bias anomaly in single layers

TL;DR

This study uses scanning tunneling microscopy and spectroscopy at ultra-low temperatures to investigate the electronic properties of layered 2H-TaSe2, revealing a zero bias anomaly in single layers and superconductivity in multilayers.

Contribution

It provides new insights into the local electronic structure of 2H-TaSe2 layers, especially the zero bias anomaly in single layers and the superconducting gap in multilayers.

Findings

Zero bias peak modulated by charge density wave

Spatially homogeneous superconducting gap in multilayers

Evidence for a zero bias anomaly in single layers

Abstract

We report a characterization of surfaces of the dichalcogenide TaSe$_2$ using scanning tunneling microscopy and spectroscopy (STM/S) at 150 mK. When the top layer has the 2H structure and the layer immediately below the 1T structure, we find a singular spatial dependence of the tunneling conductance below 1 K, changing from a zero bias peak on top of Se atoms to a gap in between Se atoms. The zero bias peak is additionally modulated by the commensurate $3a_0 \times 3a_0$ charge density wave of 2H-TaSe$_2$. Multilayers of 2H-TaSe$_2$ show a spatially homogeneous superconducting gap with a critical temperature also of 1 K. We discuss possible origins for the peculiar tunneling conductance in single layers.