# All 3d electron-hole bilayers in CrN/MgO(111) multilayers

## TL;DR

This study uses ab initio calculations to demonstrate that CrN/MgO(111) multilayers can host nanoscale, spatially separated electron and hole gases with high thermopower, promising for thermoelectric applications.

## Contribution

It reveals the formation of 2D electron and hole gases in CrN/MgO multilayers and predicts their thermoelectric properties, a novel insight into transition metal heterostructures.

## Key findings

- Large thermopower of about 250 μV/K at room temperature.
- Potential to generate 1 V voltage with 40 bilayers at 50K temperature difference.
- Nanoscale, scalable heterostructures with combined thermoelectric efficiency.

## Abstract

CrN/MgO(111) multilayers modeled via \textit{ab initio} calculations give rise to nanoscale, scalable, spatially separated two-dimensional electron and hole gases (2DEG+2DHG), each confined to its own CrN interface. Due to the Cr $3d^3$ configuration, both electron and hole gases are based on correlated transition metal layers involving bands of $3d$ character. Transport calculations predict each subsystem will have a large thermopower, on the order of 250 $\mu$$V /K$ at room temperature. These heterostructures combine a large thermoelectric efficiency with scalable nanoscale conducting sheets; for example, operating at a temperature difference of 50K, 40 bilayers could produce a 1 V voltage with a film thickness of 100 nm.