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HL: Fachverband Halbleiterphysik

HL 68: II-VI Semiconductors: mainly Optical Properties

HL 68.1: Vortrag

Freitag, 26. März 2010, 11:30–11:45, H17

Dynamical control of Mn spin system cooling by photogenerated carriers in (Zn,Mn)Se/BeTe heterostructures — •Daniel Dunker¹, J. Debus¹, A. A. Maksimov², D. R. Yakovlev¹, I. I. Tartakovskii², and M. Bayer¹ — ¹Experimentelle Physik II, Technische Universität Dortmund, 44227 Dortmund, Germany — ²Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia

We study magnetization dynamics in undoped Zn_0.99Mn_0.01Se/BeTe type-II quantum wells by means of time-resolved pump-probe-control and photoluminescence techniques. Measurements at a magnetic field of 3 T and a temperature of 1.8 K show under pulsed excitation of a control laser a strong decrease of the excitonic giant Zeeman shift which leads to a reduction of the Mn ion spin temperature. Its dynamics was studied with a nanosecond time resolution.

The band alignment of the type-II heterostructure results in a spatial separation of the thermalized electrons and holes in the (Zn,Mn)Se and BeTe layers, respectively, and this causes long radiative lifetimes of photocreated electrons. The magnetization relaxation of the Mn spin system is accelerated by the efficient transfer of spin and energy from the Mn ions to the lattice via the electrons localized in (Zn,Mn)Se layers. The strength of the laser induced cooling effect is controlled with the optical excitation density. The overall temporal evolution of the Mn spin system cooling is also influenced by the heating impact on the Mn ions of the holes, localized in BeTe, as well as by non-equilibrium phonons.