Ge as an orbitronic platform: giant in-plane orbital magneto-electric effect in a 2-dimensional hole gas

TL;DR

This paper demonstrates that germanium (Ge) 2D hole gases exhibit a giant in-plane orbital magneto-electric effect, making them promising for energy-efficient orbitronic devices by efficiently generating orbital angular momentum.

Contribution

It reports the first calculation of a large orbital magneto-electric effect in Ge 2D hole gases, highlighting their potential for orbitronic applications.

Findings

OAM density of ~10^{12} ħ/cm^2 at 10^4 V/m electric field

OME in Ge 2DHGs is an order of magnitude larger than Rashba-Edelstein effect

OAM aligned in-plane due to transitions between heavy and light hole states

Abstract

Increasing demand for computational power has initiated the hunt for energy efficient and stable memory devices. This is the overarching motivation behind the recent rise of \textit{orbitronics}, which looks to harness the orbital angular momentum of charge carriers in computing devices. Orbitronic devices require materials with efficient generation of orbital angular momentum (OAM). In 2D materials, OAM can be electrically generated via the orbital magneto-electric effect (OME). In this paper we report the calculation of the OME in 2 dimensional hole gases (2DHGs). We show that the OME in Ge holes is very large, for an applied electric field of the order $10^4$ V$/$m the OAM density is of the order $10^{12}$ $\hbar/$cm$^{2}$. Furthermore, we find the OME to be an order of magnitude larger than the Rashba-Edelstein effect in 2DHGs. The OME we calculated in 2DHGs generates OAM aligned in the plane and arises due to transitions between heavy and light hole states, which is unique to this system. Our results put Ge, as well as other p-type semiconductors, forward as strong candidates for building future orbitronic devices.