Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)

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Accueil > La Recherche > Axes & Equipes > Physique de l’Exciton, du Photon & du Spin > Optique des états collectifs et des spins (OECS) > Dynamique de Spin

Spin Noise spectroscopy and Nuclear spin

par PEPS - publié le

Spin noise spectroscopy (SNS) is a powerful new method for studying magnetic resonance and spin dynamics. It is based on measuring magnetization noise of a paramagnet using the Faraday rotation technique. We have contributed to the development of this technique, by increasing both its sensitivity and accessible frequency range using heterodyne detection scheme [Cronenberger2016]. The SNS implemented in L2C allowed, in particular, for the detection of atomic-like spin fluctuations of Mn ions diluted in CdTe, while previously SNS was limited to carriers in semiconductor heterostructures [Cronenberger2015]. This activity benefits from long-standing collaboration with institute Néel.

In a set of theoretical and experimental works we have established the potential of the SNS for probing nuclear spin polaron, a collective electron-nuclei spin state which is specific to semiconductors. To do so, we have addressed experimentally and theoretically nuclear spin relaxation in both n and p-type GaAs, as a function of impurity concentration and magnetic field (collaboration with C2N and SpinOptics Lab in St-Petersburg). The adiabatic demagnetization of nuclei to zero magnetic field, detected by SNS, provided us with a first direct confirmation of the nuclear spin temperature hypothesis, and a direct measurement of the local nuclear field [Vladimirova2018]. The figure presents the color-encoded spin noise spectra for n-GaAs (in the signal to shot noise ratio units) measured during 11 s adiabatic re-magnetization procedure ; Dashed line is calculated within a nuclear spin temperature model, accounting for relaxation. We have found that quadrupole effects affect significantly both local fields in heterostructures and nuclear spin warm-up. Record value of the nuclear spin temperature in semiconductors of 2µK has been reached.
This topic has been developed within the framework ANR SNS, PRC Russie SpinCool.

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