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Tarasenko, S. A.; Ivchenko, E. L.; Belkov, Vassilij; Ganichev, Sergey; Schowalter, D.; Schneider, Petra; Sollinger, M.; Prettl, Wilhelm; Ustinov, V. M.; Zhukov, A. E.; Vorobjev, L. E.

doi:10.1023/a:1023614814593

Cited by 15 publications

(4 citation statements)

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“…However, processes with the intermediate state in the valence band give rise to spin selectivity in exactly the same way as for interband transitions, so that a small fraction of electrons become polarized. In GaAs the number of spins per absorption was estimated to be about 10 ÿ6 for h 10 meV [25], but in our case this is about 2500 times larger due to the larger spin-orbit coupling & smaller gap of InSb, and the larger pump photon energy. The probe was left exactly as before, at 6 m, and therefore had the same sensitivity to spin polarization in the sample as for the interband pumping experiment.…”

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confidence: 51%

“…At this wavelength, well below the band gap of InSb, the strongest absorption process is free-carrier (Drude) absorption of the electrons. It has previously been shown that this process can be used to generate spin polarizations though with a rather weaker selection rule than for interband transitions [25]. Free-carrier absorption is a second order process that involves electron-photon absorption to an intermediate state, followed by phonon scattering.…”

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Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

et al. 2006

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We have used two-color time-resolved spectroscopy to measure the relaxation of electron spin polarizations in a bulk semiconductor. The circularly polarized pump beam induces a polarization either by direct excitation from the valence band, or by free-carrier (Drude) absorption when tuned to an energy below the band gap. We find that the spin relaxation time, measured with picosecond time resolution by resonant induced Faraday rotation in both cases, increases in the presence of photogenerated holes. In the case of the material chosen, n-InSb, the increase was from 14 to 38 ps. DOI: 10.1103/PhysRevLett.96.096603 PACS numbers: 72.25.Rb, 72.25.Fe, 78.47.+p Spin polarizations have become a focus of interest in semiconductor physics in recent years, not least for their potential application in ''spintronic'' devices [1]. It has been shown that spin polarized electrons (or holes) can be injected from magnetic semiconductor materials into semiconductors [2,3], that they can be coherently transported through a device [4], and that they can be controlled (or modulated) with an external electric field [5]. It remains challenging to improve these breakthroughs to the extent that they can be combined in a practical device [1]. A sufficiently long spin lifetime s is important in the design of structures which confine and/or transfer spin. It is therefore necessary to understand the establishment of a polarized spin population and subsequent spin relaxation mechanisms in both bulk and low dimensional semiconductors. A large amount of literature has been established to determine spin lifetimes by one or another form of timeresolved optical orientation techniques based on spin injection by pulsed interband pumping with circularly polarized light [4 -13]. In this Letter we investigate and contrast the spin relaxation lifetimes as measured in a bipolar (interband) experiment with spin lifetimes measured in a monopolar regime. In the former, significant numbers of excess electrons and holes are photopumped, whereas most device proposals involve electrical injection and manipulation of one type of charge carrier only, ideally at room temperature and often zero magnetic field. To this end we compare in such conditions the results of interband versus intraband pumping of spins with picosecond pulses, in the same sample. We find that the difference is a factor of between 2 to 3.Only one previous experiment measured the lifetime of spins pumped with monopolar excitation in zero magnetic field. In that case hole lifetimes in p-type GaAs=AlGaAs quantum wells were measured at low temperature by steady state bleaching of the circularly polarized photocurrent response [14]. The spin lifetime estimated from the saturation intensity was found to be 20 ps at liquid helium temperature. Our picosecond time-resolved measurements do not rely on theoretically derived absorption cross sections, were made on material at room temperature, and directly compare the bipolar and monopolar spin excitation and relaxation in the same sample. Our results...

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Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

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“…Note that the spin-galvanic current is of the same order as the background current (see [25]). The nonequilibrium in-plane spin polarization S k is prepared as described recently [21]: Circularly polarized light at normal incidence on the 2DEG plane, induces indirect (Drude-like) electron transitions in the lowest conduction subband of our n-type samples resulting in a monopolar spin orientation [26] in the z direction [ Fig. 2(b)].…”

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Experimental separation of Rashba and Dresselhaus spin-splittings

Ганичев¹,

Schneider²,

Giglberger³

et al. 2005

AIP Conference Proceedings

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The relative strengths of Rashba and Dresselhaus terms describing the spin-orbit coupling in semiconductor quantum well (QW) structures are extracted from photocurrent measurements on n-type InAs QWs containing a two-dimensional electron gas (2DEG). This novel technique makes use of the angular distribution of the spin-galvanic effect at certain directions of spin orientation in the plane of a QW. The ratio of the relevant Rashba and Dresselhaus coefficients can be deduced directly from experiment and does not relay on theoretically obtained quantities. Thus our experiments open a new way to determine the different contributions to spin-orbit coupling.

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“…We note that the observation of the mid-infrared and terahertz radiation excited spin-galvanic effect, which is due to spin orientation, gives clear evidence that direct intersubband and Drude absorption of circularly polarized radiation result in a monopolar spin orientation. Mechanisms of the monopolar spin orientation were analyzed in [18,19].…”

Section: Magneto-gyrotropic Effect Due To the Larmor-precession-induc...mentioning

confidence: 99%

Magneto-gyrotropic effects in semiconductor quantum wells

Belkov¹,

Ganichev²

2008

Semicond. Sci. Technol.

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Magneto-gyrotropic photogalvanic effects in quantum wells are reviewed. We discuss experimental data, results of phenomenological analysis and microscopic models of these effects. The current flow is driven by spin-dependent scattering in low-dimensional structures gyrotropic media resulted in asymmetry of photoexcitation and relaxation processes. Several applications of the effects are also considered.

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Cited by 15 publications

References 4 publications

Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

Experimental separation of Rashba and Dresselhaus spin-splittings

Magneto-gyrotropic effects in semiconductor quantum wells

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