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TT: Fachverband Tiefe Temperaturen

TT 28: Transport - Poster Session

TT 28.52: Poster

Thursday, March 29, 2007, 14:00–17:45, Poster A

Probing Spin Precession by Noise Spectroscopy — •Matthias Braun¹, Jürgen König¹, and Jan Martinek² — ¹TPIII, Ruhr-Universität Bochum, 44780 Bochum, Germany — ²IMP, Polish Academy of Science, 60-179 Poznań, Poland

We theoretically discuss the possibility to observe electron-spin precession by its imprint on the noise spectrum of a reference quantity. A finite-frequency noise measurement of this reference quantity can therefore be used as unorthodox electron-spin resonance experiment. We review two different systems illustrating this idea.
1.) In a single-level quantum dot with ferromagnetic leads, the spin noise is mapped on the current noise by tunnel magnetoresistance [1]. The current-noise frequency spectrum then reveals Larmor frequency and spin life time of the conduction electrons. This transport experiment is therefore equivalent to a single spin cw-ESR experiment.
2.) By sending laser light through selected semiconductor [2] or gas [3] samples, one can observe a Faraday rotation of the polarization plane. In addition, the spin fluctuations in the sample also lead to fluctuations of the Faraday rotation. These fluctuations can again be measured, and used as ESR experiment. It is even possible to realize Faraday-rotation fluctuation experiments, which avoid some sources of inhomogeneous line broadening [4].
 [1] M. Braun et al., Phys. Rev. B 74, 075328 (2006).
 [2] M. Oestreich et al., Phys. Rev. Lett. 95, 216603 (2005).
 [3] S. A. Crooker et al., Nature 431, 49 (2004).
 [4] M. Braun et al., cond-mat/0601607.