Spatial structure of Mn-Mn acceptor pairs in GaAs

TL;DR

This study combines experimental STM mapping and theoretical models to analyze the spatial structure of Mn-Mn acceptor pairs in GaAs, revealing persistent wavefunction shapes and implications for ferromagnetism.

Contribution

It provides a detailed comparison of experimental and theoretical insights into Mn-Mn pairs, highlighting wavefunction resilience and anisotropic overlaps affecting magnetic properties.

Findings

Mn-acceptor wavefunction shape persists at short Mn-Mn distances

Wavefunction anisotropy influences Curie temperatures in Mn-doped layers

Impurity-band formation plays a key role in ferromagnetism

Abstract

The local density of states of Mn-Mn pairs in GaAs is mapped with cross-sectional scanning tunneling microscopy and compared with theoretical calculations based on envelope-function and tight-binding models. These measurements and calculations show that the crosslike shape of the Mn-acceptor wavefunction in GaAs persists even at very short Mn-Mn spatial separations. The resilience of the Mn-acceptor wave-function to high doping levels suggests that ferromagnetism in GaMnAs is strongly influenced by impurity-band formation. The envelope-function and tight-binding models predict similarly anisotropic overlaps of the Mn wave-functions for Mn-Mn pairs. This anisotropy implies differing Curie temperatures for Mn $\delta$-doped layers grown on differently oriented substrates.