Electric manipulation of the Mn-acceptor binding energy and the Mn-Mn exchange interaction on the GaAs (110) surface by nearby As vacancies

TL;DR

This study theoretically explores how nearby arsenic vacancies influence the electronic and magnetic properties of manganese impurities on the GaAs (110) surface, revealing potential for local electric control of magnetic interactions.

Contribution

It introduces a microscopic tight-binding model to analyze the effects of charged arsenic vacancies on Mn acceptor binding energy and exchange interactions on GaAs surfaces.

Findings

Charged As vacancies significantly reduce Mn-acceptor binding energy when close.

Charged vacancies enhance exchange interaction between Mn impurities.

Neutral vacancies do not affect the exchange splitting.

Abstract

We investigate theoretically the effect of nearby As (arsenic) vacancies on the magnetic properties of substitutional Mn (manganese) impurities on the GaAs (110) surface, using a microscopic tight-binding model which captures the salient features of the electronic structure of both types of defects in GaAs. The calculations show that the binding energy of the Mn-acceptor is essentially unaffected by the presence of a neutral As vacancy, even at the shortest possible ${\rm V}_{\rm As}$--Mn separation. On the other hand, in contrast to a simple tip-induced-band-bending theory and in agreement with experiment, for a positively charged As vacancy the Mn-acceptor binding energy is significantly reduced as the As vacancy is brought closer to the Mn impurity. For two Mn impurities aligned ferromagnetically, we find that nearby charged As vacancies enhance the energy level splitting of the associated coupled acceptor levels, leading to an increase of the effective exchange interaction. Neutral vacancies leave the exchange splitting unchanged. Since it is experimentally possible to switch reversibly between the two charge states of the vacancy, such a local electric manipulation of the magnetic dopants could result in an efficient real-time control of their exchange interaction.