Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: Poster Session: Spintronics; Spin-controled transport; Topological insulators; Interfaces / Surfaces; Magnetic semiconductors

HL 29.1: Poster

Montag, 11. März 2013, 16:00–20:00, Poster A

Spin noise spectroscopy at ultra low temperatures — •Jan Gerrit Lonnemann, Jens Hübner, and Michael Oestreich — Institute for Solid State Physics, Leibniz Universität Hannover, Appelstr. 2, D-30167 Hannover, Germany

In recent years the all optical method of semiconductor spin noise spectroscopy (SNS) has proven to be a powerful tool to investigate spin dependent processes in semiconductors [1]. Especially at low temperatures most optical methods obscure the real spin dynamics due to carrier heating and excitation. SNS on the other hand utilizes off-resonant Faraday rotation for probing the intrinsic spin fluctuations at thermal equilibrium.

Consequently SNS is ideally suited to analyze systems at ultra low temperatures due to its perturbation free nature. We present measurements performed at temperatures as low as 100 mK. At these very low temperatures we try to gain access to spin physics obscured otherwise like for example quantum phase transitions, magnetic ordering, or highly localized states. The investigated GaAs sample is doped slightly below the metal-to-insulator transition [2] and shows localization of the donor electrons especially below 1 K. We observe a strong negative shift of the electron g-factor with increasing temperature while in the same sample the opposite dependence is observed above 10 K, where the donors are delocalized. The intrinsic spin lifetime of the weakly localized electrons is measured to be well above 300 ns.

[1] G.M. Müller, et al., Physica E 43, 569 (2010).

[2] M. Römer, et al., Phys. Rev. B 81, 075216 (2010).