Interaction of electron and nuclear spins in semiconductors became more important over the last few years for spin-based quantum information. However, the knowledge to understand the exact spin dynamics of such a complex system is not complete. We study this interaction in a set of n-doped bulk GaAs.
We measure the electron spin relaxation (ESR) time τs via the Hanle method in an external magnetic field ( Bext) at 6.5 K. To have a complete quantitative picture of the intrinsic di ffusion processes of the electrons around the metal-insulator transition (MIT), magnetotransport meas- urements were carried out for a full range of temperature up to 300 K. The result of the measured temperature dependence of the conductivity together with the inverse Hall resistance give us all the required parameters for ESR. Just below the MIT, there is a maximum for a spin lifetime of more than 800 ns which is the result of hyper fine interaction (HFI) and spin decoherence due to hopping. At MIT, the HFI together with variable range hopping (VRH), and Dyakonov-Perel (DP) mechanisms lead to spin relaxation while for high doped samples, just DP is the most dominant mechanism. Additionally, we want to achieve a temperature dependency of τs to have a better understanding of our samples.
Moreover, nuclear polarization is the result of the HFI between electrons and lattice nuclei. This has an effective nuclear fi eld, BN, which acts on electron spins in the same way as a Bext. Employing extra information from the transport measurements, we establish a full picture of the nuclear spin relax- ation time and its dependency to Bext, nd and T. The results give us an insight into the nuclear spin thermodynamics. The ongoing project is to de fine a complete theoretical model based on the mechanisms of the nuclear spin system.
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30167 Hannover