Ref HAL: hal-01909323_v1
Exporter : BibTex | endNote
Résumé:

In the recent years the spectroscopy of spin noise has won its spurs for spin dynamics related studies in semiconductors, largely because it exhibits several quite attractive features. Noticeably it enables almost perturbation-free detection of spontaneous electron spin fluctuations. In addition as the amplitude of spin noise grows when the size of the probed region is reduced, it is well adapted for spatially resolved studies. Also the spin noise spectrum is quite sensitive to internal effective fields, which allows to probe locally the existence of nuclear fields. Finally, the combination of spin noise spectroscopy and optical heterodyning has been demonstrated, which permits enhanced sensitivity and broadband detection, while keeping a high spectral resolution [1].In this poster we will present results obtained by heterodyne detection of spin noise in an n-doped CdTe epilayer with donor density n∼3×〖10〗^17cm-3. Thanks to the enhanced sensitivity gained by heterodyne detection we could detect the spin noise of electrons bound to neutral donors for probe powers as low as 5 µW. In these conditions we observe an extremely slow hopping rate W0 of electron spin between neighbouring donors, and extremely slow electron spin relaxation rate s (see Figure 1). The observed noise spectrum at zero field is characteristic of electron spin precession in the frozen nuclear field acting on the electrons bound to the donors and exhibits two components. A central lorentzian line corresponding to the electron spin component along the nuclear field, and two satellites gaussian lines corresponding to the spin precession in the nuclear field. We analyze our results in the framework of a theoretical model, which takes into account both the electron spin precession, and the hopping between donors, but slightly modified to take into account an eventual non-zero nuclear spin polarization [2]. In agreement with the theory we can see that the satellites merge with the central line as the hopping rate increases (at the highest probe power). Surprisingly W0 and s become quite small at the lowest probe power. We find that the electron spin relaxation time becomes longer than 1 µs in this regime.

DOI: 10.1103/PhysRevB.97.041301
WoS: WOS:000419471200001
5 Citations
Résumé:

We develop a method of nonperturbative optical control over adiabatic remagnetization of the nuclear spin system and apply it to verify the spin temperature concept in GaAs microcavities. The nuclear spin system is shown to exactly follow the predictions of the spin temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalization. These findings open a way for the deep cooling of nuclear spins in semiconductor structures, with the prospect of realizing nuclear spin-ordered states for high-fidelity spin-photon interfaces.

Résumé:

The concept of nuclear spin temperature is one of the cornerstones of the nuclear magnetism in solids. It has made possible realisation of the cryogenic cooling into the microKelvin range and observation of nuclear spin ordering in metals and insulators [1]. However, proving its validity for semiconductor nano- and microstructures is challenging due to the lack of techniques capable of precise sensing of weak nuclear magnetisation in a small volume. We develop a method of non-perturbative optical control over adiabatic remagneti- sation of the nuclear spin system in semiconductors and apply it to study nuclear spin thermodynamics in GaAs microcavities. The nuclear spin system is found to exactly follow the predictions of the spin-temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalisation [2]. These ndings open a way to deep cooling of nuclear spins in semiconductor structures, with a prospect of realisation of nuclear spin-ordered states for high delity spin-photon interfaces. References [1] A. S. Oja, O. V. Lounasmaa, Rev. Mod. Phys 69, 1 (1997). [2] P. Maletinsky, M. Kroner, A. Imamoglu, Nat. Phys 5, 407 (2009).

Résumé:

Semiconductor coupled quantum wells (CQWs) offer an excellent laboratory for studying both intra-well direct excitons (DX) and inter-well indirect excitons (IX), as well as their interactions and spin dynamics. The presentation will focus on the pump-probe spectroscopy, a powerful tool of nonlinear optics, that we have applied to biased CQW. We will show how DX and IX spin and population dynamics, as well as the spin polarization of residual electrons may be detected via the modulation of reflectivity and Kerr rotation spectra. In particular, the origin of the nonlinearities related to the low oscillator strength IXs will be addressed. Spin relaxation and decoherence mechanisms for DX, IX and electron gas will be presented. Results on IXs created via magnetic Stark effect and the resulting spin dynamics in unbiased quantum wells will be discussed

Ref HAL: hal-01629354_v1
Ref Arxiv: 1706.02528
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

We develop a method of non-perturbative optical control over adiabatic remagnetisation of the nuclear spin system and apply it to verify the spin temperature concept in GaAs microcavities. The nuclear spin system is shown to exactly follow the predictions of the spin-temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalisation. These findings open a way to deep cooling of nuclear spins in semiconductor structures, with a prospect of realisation of nuclear spin-ordered statesfor high fidelity spin-photon interfaces.

Commentaires: 7 pages, 4 figures

Ref HAL: hal-01523113_v1
DOI: 10.1103/PhysRevB.95.125312
WoS: WOS:000399218900003
Exporter : BibTex | endNote
8 Citations
Résumé:

Nuclear spin relaxation is studied in n-GaAs thick layers and microcavity samples with different electron densities.We reveal that both in metallic samples where electrons are free and mobile, and in insulating samples where electrons are localized, nuclear spin relaxation is strongly enhanced at low magnetic fields. The origin of this effect could reside in the quadrupole interaction between nuclei and fluctuating electron charges, that has been proposed to govern nuclear spin dynamics at low magnetic fields in the insulating samples. The characteristic values of these magnetic fields are given by dipole-dipole interaction between nuclei in bulk samples, and are greatly enhanced in microcavities, presumably due to additional strain, inherent to microstructures and nanostructures.

Ref HAL: hal-01397602_v1
DOI: 10.1063/1.4962863
WoS: WOS:000385634500012
Exporter : BibTex | endNote
11 Citations
Résumé:

Spin noise spectroscopy is a powerful technique for studying spin relaxation in semiconductors. Inthis article, we propose an extension of this technique based on optical heterodyne detection of spinnoise, which provides several key advantages compared to conventional spin noise spectroscopy:detection of high frequency spin noise not limited by detector bandwidth or sampling rates of digitizers,quantum limited sensitivity even in case of very weak probe power, and possible amplificationof the spin noise signal. Heterodyne detection of spin noise is demonstrated on insulating n-dopedGaAs. From measurements of spin noise spectra up to 0.4 Tesla, we determined the distribution ofg-factors, Δg/g = 0.49%.