Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 95: Poster IV B (Quantum dots and wires: Prepration, characterization, optical properties, and transport)
HL 95.23: Poster
Thursday, March 19, 2015, 14:00–20:00, Poster B
Spin switching in Mn-doped quantum dots using detuned and chirped laser pulses — •Sebastian Lüker1, Doris E. Reiter1,2, Vollrath Martin Axt3, and Tilmann Kuhn1 — 1Institut für Festkörpertheorie, WWU Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2Blackett Laboratory, Imperial College, London, UK — 3Theoretische Physik III, Universität Bayreuth
When a manganese (Mn) ion is doped into a CdTe quantum dot (QD), the photoluminescence spectrum shows six lines corresponding to the six Mn spin states. This is caused by the exchange interaction which couples the Mn spin to the spin of the exciton in the QD. This coupling enables the control of the Mn spin via the optical manipulation of the exciton. For excitation with circularly polarized laser pulses, the complete system can be reduced to a bunch of three level systems, consisting of the ground state with Mn spin in a given orientation, the bright exciton state with unchanged Mn spin, and the dark exciton state with flipped Mn spin.
We present a theoretical analysis of two different switching protocols for the Mn spin. The first one uses an ultrashort resonant laser pulse which excites the exciton. By applying a second pulse, which is detuned from the exciton transition energy, the relevant states are shifted into resonance, resulting in an occupation transfer between the Mn spin states. An alternative switching protocol uses chirped, i.e., frequency modulated laser pulses. In this case, one pulse is sufficient to manipulate the Mn spin. During the pulse, the state of the system is driven adiabatically into the desired Mn spin state.