# An atomically thin oxide layer on the elemental superconductor Ta(001) surface

## TL;DR

This study combines experimental and ab initio methods to analyze the atomic and electronic structures of a reconstructed oxygen-tantalum surface, revealing metastable superstructures and their electronic origins relevant for Majorana physics applications.

## Contribution

It identifies two metastable superstructures on the Ta(001)-O surface, explains contrast reversal mechanisms, and links surface oxygen states to electronic properties and potential adsorption behaviors.

## Key findings

- Discovered two metastable superstructures on Ta(001)-O surface.
- Identified electronic origin of contrast reversal at positive bias.
- Linked oxygen states to surface electronic properties and adsorption.

## Abstract

Recently the oxygen-reconstructed tantalum surface Ta(001)-p(3$\times$3)-O has experienced considerable attention due its use as a potential platform for Majorana physics in adatom chains. Experimental studies using scanning tunneling microscopy and spectroscopy found rich atomic and electronic structures already for the clean Ta(001)-O surface, which we combine here with $ab~initio$ methods. We discover two metastable superstructures at the root of the different topographic patterns, discuss its emergence during annealing, and identify the electronic properties. The latter is determined as the sole origin for the contrast reversal seen at positive bias. The observed effects are essentially connected to the two distinct oxygen states appearing on the surface in different geometries. The second superstructure was found in simulations by introducing oxygen vacancies, what was also observed in tantalum pentoxide systems. Additionally we study the charge distribution on the oxidized surface and underline its importance for the adsorption process of polarizable atoms and molecules.