Spin-Sensitive Bleaching and Monopolar Spin Orientation in Quantum Wells

Ganichev, Sergey; Danilov, Sergey; Belkov, Vassilij; Ivchenko, E. L.; Bichler, Max; Wegscheider, Werner; Weiss, Dieter; Prettl, Wilhelm

doi:10.1103/physrevlett.88.057401

Cited by 68 publications

(70 citation statements)

References 31 publications

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“…The microscopic picture given above requires that the generated current is spin polarized and suggests that the system can be considered as a source for spin-polarized currents. The e ect, being sensitive to the degree of spin orientation, provides an easy access to spin dynamics in semiconductor structures [14,15]. In addition to the circular photogalvanic e ect the linear photogalvanic e ect and the photon drag e ect have been observed in QWs of both nand p-type.…”

Section: Discussionmentioning

confidence: 96%

Photogalvanic effects in quantum wells

Ganichev¹,

Ivchenko²,

Prettl³

2002

Physica E: Low-dimensional Systems and Nanostructures

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Circular and linear photogalvanic e ects induced by far-infrared radiation have been investigated in both n-type and p-type quantum wells (QWs) of various point symmetry groups. The circular photogalvanic e ect arises due to optical spin orientation of free carriers in QWs which results in a directed motion of free carriers in the plane of a QW perpendicular to the direction of light propagation. Due to selection rules the direction of the current is determined by the helicity of the light and can be reversed by switching the helicity from right to left. ?

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Section: Discussionmentioning

confidence: 96%

Photogalvanic effects in quantum wells

Ganichev¹,

Ivchenko²,

Prettl³

2002

Physica E: Low-dimensional Systems and Nanostructures

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“…In the limit of high impedance (Zϭϱ) spin is detected by measuring the voltage V s ϳ␦M developed across the N/F2 interface; (c) spin accumulation in a device in which a superconductor (with the superconducting gap ⌬) is occupying the region between F1 and F2. (Ganichev et al, 2001;Ganichev, Danilov, et al, 2002;Ganichev et al, 2003), is given by Ganichev and Prettl (2003).…”

Section: Fig 5 (mentioning

confidence: 99%

Spintronics: Fundamentals and applications

2004

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Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics. CONTENTS

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“…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.…”

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confidence: 99%

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-Sensitive Bleaching and Monopolar Spin Orientation in Quantum Wells

Cited by 68 publications

References 31 publications

Photogalvanic effects in quantum wells

Photogalvanic effects in quantum wells

Spintronics: Fundamentals and applications

Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

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