Transmission spectra of Fe/MgO (001) double-barrier tunnel junctions at finite bias

TL;DR

This paper investigates how bias voltage influences the transmission spectra of Fe/MgO (001) single- and double-barrier tunnel junctions, revealing the sensitivity of resonant tunneling states to applied bias.

Contribution

It provides a self-consistent, ab initio analysis of bias-dependent transmission spectra in Fe/MgO tunnel junctions using density functional theory and Green's functions.

Findings

Resonant tunneling states are sensitive to bias voltage.

Bias rapidly destroys surface state-mediated transport in single barriers.

Quantum well state tunneling in double barriers is strongly affected by bias.

Abstract

In this contribution, we calculate in a self-consistent way the ballistic transmission as a function of energy of one Fe/MgO (001) single-barrier and one double-barrier tunnel junction, relating them to their electronic structure. The transmission spectra of each kind of junction is calculated at different applied bias voltages. We focus on the impact that bias has on the resonant tunneling mediated by surface and quantum well states. The calculations are done in the coherent regime, using a combination of density functional theory and non-equilibrium Green's functions, as implemented in the {\it ab initio} code {\it SMEAGOL}. We conclude that, for both kinds of junction, the transmission functions depend on the applied bias voltage. In the single-barrier junction, transport mediated by resonant Fe minority surface states is rapidly destroyed by bias. In the double-barrier junction, the appearance of resonant tunneling through majority quantum well states is strongly affected by bias.