Regensburg 2007 – wissenschaftliches Programm

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SYSS: Symposium Spins in Semiconductors

SYSS 1: Spins in Semiconductors

SYSS 1.6: Hauptvortrag

Montag, 26. März 2007, 11:20–11:40, H1

A microscopic view of the magnetism in magnetic semiconductors (replaces the contribution by N. Samarth) — •Michael Flatté — Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242-1479, USA

Ferromagnetism in carrier-mediated dilute magnetic semiconductors arises from the interaction of localized spins with holes. In the ferromagnetic semiconductor GaMnAs both the localized spins and the holes come from the magnetic dopant Mn. The microscopic nature of ferromagnetism in GaMnAs can be directly probed with scanning tunneling microscopy (STM) in samples with very low concentrations of Mn ions. Theoretical predictions[1] of a very spatially anisotropic wave function for a hole bound to a Mn ion have been confirmed[2] by STM images of the hole wave function in GaAs dilutely doped with Mn. Spatial overlap of these Mn-associated hole wave functions produces an effective spin-spin interaction, and eventually ferromagnetism. The highly anisotropic wave functions lead to highly anisotropic spin-spin interaction energies[1], which have been recently observed[3] in GaAs doped atom-by-atom with Mn in precise pair configurations. Control of the hole wave function with electric fields may lead also to new ways to encode and manipulate quantum information in Mn ionic spins[4].

[1] J.-M. Tang and M. E. Flatté, Phys. Rev. Lett. 92, 047201 (2004).

[2] A. Yakunin, et al., Phys. Rev. Lett. 92, 216806 (2004).

[3] D. Kitchen, A. Richardella, J.-M. Tang, M. E. Flatté, and A. Yazdani, Nature 442, 436 (2006).

[4] J.-M. Tang, J. Levy and M. E. Flatté, Phys. Rev. Lett. 97, 106803 (2006).

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