Strong influence of the complex bandstructure on the tunneling electroresistance: A combined model and ab-initio study

TL;DR

This study demonstrates how the complex bandstructure significantly influences tunneling electroresistance in ferroelectric tunnel junctions, combining ab-initio calculations with a macroscopic electrostatic model to reveal sign reversals linked to the imaginary Fermi velocity.

Contribution

It introduces a combined ab-initio and macroscopic modeling approach to connect complex bandstructure with TER behavior, highlighting the role of the imaginary Fermi velocity.

Findings

Sign reversal of TER ratio depending on chemical potential.

The imaginary Fermi velocity explains the microscopic origin of TER effects.

Complex bandstructure analysis provides detailed transport insights.

Abstract

The tunneling electroresistance (TER) for ferroelectric tunnel junctions (FTJs) with BaTiO_{3} (BTO) and PbTiO}_{3} (PTO) barriers is calculated by combining the microscopic electronic structure of the barrier material with a macroscopic model for the electrostatic potential which is caused by the ferroelectric polarization. The TER ratio is investigated in dependence on the intrinsic polarization, the chemical potential, and the screening properties of the electrodes. A change of sign in the TER ratio is obtained for both barrier materials in dependence on the chemical potential. The inverse imaginary Fermi velocity describes the microscopic origin of this effect; it qualitatively reflects the variation and the sign reversal of the TER. The quantity of the imaginary Fermi velocity allows to obtain detailed information on the transport properties of FTJs by analyzing the complex bandstructure of the barrier material.