Bias-voltage dependence of the magneto-resistance in ballistic vacuum tunneling: Theory and application to planar Co(0001) junctions

TL;DR

This paper develops a heuristic model for bias-voltage dependence in ballistic vacuum tunneling, applying it to Co(0001) junctions and explaining the absence of zero-bias anomalies.

Contribution

It introduces a parameterized tunnel-barrier shape approach that combines heuristic bias treatment with first-principles electrode descriptions.

Findings

Parameterization of tunnel barriers for vacuum tunneling.

Application to Co(0001) junctions.

Explanation of zero-bias anomaly absence.

Abstract

Motivated by first-principles results for jellium and by surface-barrier shapes that are typically used in electron spectroscopies, the bias voltage in ballistic vacuum tunneling is treated in a heuristic manner. The presented approach leads in particular to a parameterization of the tunnel-barrier shape, while retaining a first-principles description of the electrodes. The proposed tunnel barriers are applied to Co(0001) planar tunnel junctions. Besides discussing main aspects of the present scheme, we focus in particular on the absence of the zero-bias anomaly in vacuum tunneling.