Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 41: Spintronics / Quantum Information: Materials and Methods (jointly with HL)
TT 41.2: Talk
Wednesday, March 13, 2013, 15:15–15:30, H2
On the misinterpretation of the temperature dependence of T2* in time-resolved Faraday rotation — •Sebastian Kuhlen1, Ralph Ledesch1, Carla Schenk1, Matthias Althammer2, Sebastian T. B. Gönnenwein2, Matthias Opel2, Rudolf Gross2, and Bernd Beschoten1 — 1II. Physikalisches Institut A, RWTH Aachen University, Aachen — 2Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching
Time-resolved Faraday rotation (TRFR) is a well-established optical pump probe technique to generate and to probe spin coherence in semiconductors. Spin dephasing times T2* can easily be determined from TRFR if their values are comparable to the available pump-probe-delay. If, however, T2* exceeds the laser repetition time resonant spin amplification (RSA) can equally be used to extract T2*. We demonstrate that in ZnO these techniques have several tripping hazards resulting in deceptive results for T2*. We show that the temperature dependence of the amplitude ratio of two separate spin species can easily be misinterpreted as a strongly temperature dependent T2* of a single spin ensemble, while the two spin species have T2* values which are nearly independent of temperature. Additionally, consecutive pump pulses can significantly diminish the
spin polarization, which remains from previous pump pulses. While this barely affects T2* values extracted from delay line scans, it results in seemingly shorter T2* values in RSA.
Work supported by DFG through SPP 1285.