Pure spin current gratings in semiconductors generated by quantum interference

Kerachian, Y.; Němec, P.; Driel, H. M. van; Smirl, Arthur L.

doi:10.1063/1.1757033

Cited by 8 publications

(7 citation statements)

References 11 publications

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“…Injection of pure spin current by the QUIC technique was originally proposed in 2000 [57] and has been demonstrated experimentally in GaAs [58,86] ZnSe [59], and Ge [87] by using a spatially resolved pump-probe technique [58,87], transientgrating technique [86], and photoluminescence [59]. Compared to other available techniques to generate pure spin currents [40,[88][89][90][91][92][93][94], the QUIC technique has two significant advantages: the current injected is ballistic and the current density can be very high.…”

Section: Optical Injection Of Ballistic Currentsmentioning

confidence: 99%

Optical studies of ballistic currents in semiconductors [Invited]

Ruzicka

Zhao

2012

J. Opt. Soc. Am. B

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We present a summary of recent studies of ballistic currents using nonlinear optical techniques. Quantum interference between one-and two-photon absorption pathways is used to inject and control ballistic currents in GaAs samples. With this, a pure charge current, pure spin current, or spin-polarized charge current can be injected by changing the polarization configuration of the two pump pulses. Such currents are temporally and spatially resolved using high-resolution pump-probe techniques, including a derivative-detection scheme, which allows detection of the motion of carriers as small as 0.1 nm. Observation of the intrinsic inverse spin Hall effect in the ballistic regime, a study of time-resolved ballistic spin-polarized charge currents, and a study of the efficiency of spin current injection by quantum interference were all achieved using these techniques. Additionally, we discuss demonstrations of second-order nonlinear optical effects induced by charge and spin currents, which allow for the nondestructive, noninvasive, and real-time imaging of currents.

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Section: Optical Injection Of Ballistic Currentsmentioning

confidence: 99%

Optical studies of ballistic currents in semiconductors [Invited]

Ruzicka

Zhao

2012

J. Opt. Soc. Am. B

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“…This variation was also observed in earlier work that dealt with spin current gratings. 17 Figure 4͑a͒ shows the time-dependent diffraction efficiency for 2 GW cm −2 , 1550 nm and 17 MW cm −2 , 775 nm noncollinearly incident pulses. Figures 4͑b͒ and 4͑c͒ show similar data for 5 GW cm −2 , 1550 nm and 140 MW cm −2 , 775 nm pump pulses.…”

Section: B Experimental Resultsmentioning

confidence: 99%

“…If, however, the pulses are noncollinearly incident on a semiconductor wafer, the phase of the optical beams varies in the plane of the material, inducing transient, spatial current gratings. Noncollinear QUIC processes were used earlier 17 to generate pure electron spin current gratings in GaAs at 300 K using 775 and 1550 nm, orthogonally polarized 150 fs pulses. The spin current grating evolves into a pure spin population grating ͑with no carrier density modulation͒ and is observed to decay by electron spin diffusion on a 3 ps time scale from the measurements of diffracted 830 nm probe pulses.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of charge current gratings generated in GaAs by ultrafast quantum interference control

et al. 2007

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Ballistic charge current gratings are induced in GaAs at 300 K by quantum interference of single-and two-photon absorption using noncollinearly incident 775 and 1550 nm, 150 fs pulses. First-order diffraction of time-delayed 830 nm, 150 fs probe pulses is used to observe carrier evolution for injected densities near 10 17 cm −3. The current grating forms electron and hole charge-density gratings during pumping, and because the pumping is uniform while the carrier density and hence electronic specific heat is not, a carrier temperature grating also forms. The peak diffraction efficiency from both grating types is only ϳ10 −9. The temperature grating, with modulation amplitude ϳ1 K, decays through cooling in ϳ500 fs. Space-charge fields neutralize the electron and hole density gratings by the end of pumping, but nonetheless leave a neutral, electron-hole pair density grating with amplitude of ϳ10 −3 of the injected carrier density. At the highest injected carrier densities, the pair grating amplitude builds on a few picosecond time scale before decaying by recombination and ambipolar diffusion with an ϳ15 ps time constant. A model based on continuity equations for carrier density, momentum, and energy during ballistic and drift motion is used to help interpret the experimental data. Besides qualitatively confirming the above dynamics, the model suggests that the pair grating amplitude and evolution is determined by two factors: ͑1͒ the warping or nonparabolicity of the hole bands and ͑2͒ the transfer of some electrons from the ⌫-valley electron-density grating to the L, X conduction band valleys during excitation, and their subsequent return to the ⌫ valley on a few picosecond time scale.

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“…have no direct way of monitoring spin currents, as we do for the charge currents through the THz radiation they emit, in order to observe them we have generated spin current gratings and observed their evolution [19]. The spin current gratings can be formed by allowing the two orthogonally polarized pump beams at 1550 nm and 775 nm to interact non-collinearly in a 1 µm thick GaAs sample.…”

Section: Conduction Bandmentioning

confidence: 99%

Coherence control of electron spin currents in semiconductors

Driel

Sipe

Smirl

2006

Physica Status Solidi (b)

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We provide an overview of some of our recent work on the use of one color and two color optical techniques to generate and control electronic spin currents in semiconductors for which a spin -orbit interaction exists. The generation process relies on the quantum interference between different absorption pathways, such as that between single and two photon absorption or those involving different polarization states of a monochromatic beam. For different crystal orientations and/or beam polarizations it is possible to generate a spin current with or without an electric current, and an electrical current with or without a spin current. In our experiments, which are conducted either at 80 K or 295 K, we typically employ nominally 100 fs pulses centered near 1500 and 750 nm. The currents generated are quasi-ballistic and the carriers typically move distances of ~1 -10 nm, determined by the momentum relaxation time, which is of the order of 100 fs. The transient characteristics of spin-polarized electrical currents generated in strained GaAs at room temperature by ~100 fs pulses is detected by the emitted THz radiation. Pure spin currents can be detected by taking advantage of the accumulation of up and down spins on opposite sides of tightly focused pump beams. The spin states are detected through differential transmission measurements of tightly focused right and left circularly polarized, near-band-edge probe pulses, delayed by several picoseconds from the pump pulses to allow carrier thermalization to occur. By spatial scanning across the differential spin profiles and determining the amplitude of the response we are able to translate this into nm spatial resolution of spin displacement. Finally, the ability to generate ballistic currents using purely optical techniques allows us to generate transverse Hall-like currents, with transverse charge currents generated from pure spin currents and transverse spin currents generated from pure charge currents.

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Pure spin current gratings in semiconductors generated by quantum interference

Cited by 8 publications

References 11 publications

Optical studies of ballistic currents in semiconductors [Invited]

Optical studies of ballistic currents in semiconductors [Invited]

Dynamics of charge current gratings generated in GaAs by ultrafast quantum interference control

Coherence control of electron spin currents in semiconductors

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