Magnetic Anisotropy of Single Mn Acceptors in GaAs in an External Magnetic Field

TL;DR

This study examines how external magnetic fields influence the electronic and magnetic properties of Mn acceptors in GaAs, revealing that the acceptor wavefunction remains localized and largely unaffected by fields up to 6 T, with deeper impurities showing more sensitivity.

Contribution

The paper combines experimental STM imaging with theoretical tightbinding calculations to analyze magnetic anisotropy and wavefunction localization of Mn acceptors in GaAs under magnetic fields.

Findings

Acceptor wavefunction is highly anisotropic and not significantly affected by magnetic fields up to 6 T.

Magnetic anisotropy landscape is significantly modified for surface and near-surface Mn acceptors.

Deeper Mn acceptors have more delocalized wavefunctions and are more sensitive to magnetic moment orientation.

Abstract

We investigate the effect of an external magnetic field on the physical properties of the acceptor hole states associated with single Mn acceptors placed near the (110) surface of GaAs. Crosssectional scanning tunneling microscopy images of the acceptor local density of states (LDOS) show that the strongly anisotropic hole wavefunction is not significantly affected by a magnetic field up to 6 T. These experimental results are supported by theoretical calculations based on a tightbinding model of Mn acceptors in GaAs. For Mn acceptors on the (110) surface and the subsurfaces immediately underneath, we find that an applied magnetic field modifies significantly the magnetic anisotropy landscape. However the acceptor hole wavefunction is strongly localized around the Mn and the LDOS is quite independent of the direction of the Mn magnetic moment. On the other hand, for Mn acceptors placed on deeper layers below the surface, the acceptor hole wavefunction is more delocalized and the corresponding LDOS is much more sensitive on the direction of the Mn magnetic moment. However the magnetic anisotropy energy for these magnetic impurities is large (up to 15 meV), and a magnetic field of 10 T can hardly change the landscape and rotate the direction of the Mn magnetic moment away from its easy axis. We predict that substantially larger magnetic fields are required to observe a significant field-dependence of the tunneling current for impurities located several layers below the GaAs surface.