The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
K. W. West - One of the best experts on this subject based on the ideXlab platform.
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Current-induced nuclear-spin activation in a Two-Dimensional Electron Gas
Physical Review B: Condensed Matter and Materials Physics, 2009Co-Authors: C. R. Dean, B. A. Piot, G. Gervais, L. N. Pfeiffer, K. W. WestAbstract:Electrically detected nuclear magnetic resonance was studied in detail in a Two-Dimensional Electron Gas as a function of current bias and temperature. We show that applying a relatively modest dc-current bias, I_dc ~ 0.5 microAmps, can induce a re-entrant and even enhanced nuclear spin signal compared with the signal obtained under similar thermal equilibrium conditions at zero current bias. Our observations suggest that dynamic nuclear spin polarization by small current flow is possible in a Two-Dimensional Electron Gas, allowing for easy manipulation of the nuclear spin by simple switching of a dc current.
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Current-induced nuclear-spin activation in a Two-Dimensional Electron Gas
Physical Review B, 2009Co-Authors: Cory Dean, B. A. Piot, G. Gervais, L. N. Pfeiffer, K. W. WestAbstract:Electrically detected nuclear magnetic resonance was studied in detail in a Two-Dimensional Electron Gas as a function of current bias and temperature. We show that applying a relatively modest dc-current bias ${I}_{\text{dc}}\ensuremath{\simeq}0.5\text{ }\ensuremath{\mu}\text{A}$ can induce an enhanced nuclear-spin signal compared with the signal obtained under similar thermal equilibrium conditions at zero current bias. Our observations suggest that dynamic nuclear-spin polarization by small current flow is possible in a Two-Dimensional Electron Gas, allowing for easy manipulation of the nuclear spin by simple switching of a dc current.
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engineering artificial graphene in a two dimensional Electron Gas
Physical Review B, 2009Co-Authors: Marco Gibertini, Vittorio Pellegrini, Achintya Singha, Marco Polini, Giovanni Vignale, Aron Pinczuk, Loren Pfeiffer, K. W. WestAbstract:At low energy, Electrons in doped graphene sheets behave like massless Dirac fermions with a Fermi velocity, which does not depend on carrier density. Here we show that modulating a Two-Dimensional Electron Gas with a long-wavelength periodic potential with honeycomb symmetry can lead to the creation of isolated massless Dirac points with tunable Fermi velocity. We provide detailed theoretical estimates to realize such artificial graphenelike system and discuss an experimental realization in a modulation-doped GaAs quantum well. Ultrahigh-mobility Electrons with linearly dispersing bands might open new venues for the studies of Dirac-fermion physics in semiconductors.
Werner Wegscheider - One of the best experts on this subject based on the ideXlab platform.
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Propagation length of mesoscopic photocurrents in a Two-Dimensional Electron Gas
Physical Review B, 2012Co-Authors: Markus Stallhofer, Werner Wegscheider, Christoph Kastl, Marcel Brändlein, Christoph Karnetzky, Dieter Schuh, Alexander W. HolleitnerAbstract:We investigate the average propagation length of photogenerated nonequilibrium Electrons in a Two-Dimensional Electron Gas using a quantum point contact as a local photocurrent detector. To this end, Electrons are photogenerated both quasiresonantly and nonresonantly to the optical interband transition in the quantum well comprising the Two-Dimensional Electron Gas. The photocurrent is analyzed as a function of the distance between the excitation spot in the Two-Dimensional Electron Gas and the detector. We find that the determined propagation length depends nonmonotonically on the laser intensity. We interpret the observation by an interplay of an enlarged scattering phase space of the photogenerated Electrons and the screening of sample specific scatterers.
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Measurement of spin-dependent conductivities in a Two-Dimensional Electron Gas
Physical Review B, 2010Co-Authors: Hadi Ebrahimnejad, Yuan Ren, Sergey Frolov, İnanç Adagideli, Joshua Folk, Werner WegscheiderAbstract:Spin accumulation is generated by injecting an unpolarized charge current into a channel of GaAs Two-Dimensional Electron Gas subject to an in-plane magnetic field, then measured in a nonlocal geometry. Unlike previous measurements that have used spin-polarized nanostructures, here the spin accumulation arises simply from the difference in bulk conductivities for spin-up and spin-down carriers. Comparison to a diffusive model that includes spin subband splitting in magnetic field suggests a significantly enhanced Electron spin susceptibility in the Two-Dimensional Electron Gas.
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Direct observation of hole edge channels in a Two-Dimensional Electron Gas
Physica E: Low-dimensional Systems and Nanostructures, 2000Co-Authors: Artur Zrenner, A. Paassen, Al. L. Efros, M. Stopa, J. Frankenberger, M. Bichler, Werner WegscheiderAbstract:In spatially resolved magneto-optical experiments we observe hole confinement at the edge of a Two-Dimensional Electron Gas and hole transport in edge channels. In a theoretical analysis we show that a repulsive edge potential for holes at the boundary of a Two-Dimensional Electron Gas is caused by a polaron effect
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DIRECT OBSERVATION OF HOLE EDGE CHANNELS IN A TWO DIMENSIONAL Electron Gas
Physical Review Letters, 1999Co-Authors: A. Paassen, Artur Zrenner, Al. L. Efros, M. Stopa, J. Frankenberger, M. Bichler, Werner WegscheiderAbstract:We report the direct optical observation of confinement and transport of minority holes in a two dimensional Electron Gas. In spatially resolved magneto-optical experiments we observe hole confinement at the edge of a two dimensional Electron Gas and hole transport in edge channels. In a theoretical analysis we show that a repulsive edge potential for holes at the boundary of a two dimensional Electron Gas is caused by a polaron effect
Amir Ordacgi Caldeira - One of the best experts on this subject based on the ideXlab platform.
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Photoluminescence spectrum of an interacting Two-Dimensional Electron Gas at ν = 1
Physical Review B, 2005Co-Authors: R. L. Doretto, Amir Ordacgi CaldeiraAbstract:We report on the theoretical photoluminescence spectrum of an interacting Two-Dimensional Electron Gas at filling factor one $(\ensuremath{\nu}=1)$. We considered a model similar to the one adopted to study the x-ray spectra of metals and solved it analytically using the bosonization method previously developed for the Two-Dimensional Electron Gas at $\ensuremath{\nu}=1$. We calculated the emission spectra of the right and the left circularly polarized radiations for the situations where the distance between the Two-Dimensional Electron Gas and the valence band hole is smaller and greater than the magnetic length. For the former, we showed that the polarized photoluminescence spectra can be understood as the recombination of the so-called excitonic state with the valence band hole whereas, for the latter, the observed emission spectra can be related to the recombination of a state formed by a spin down Electron bound to $n$ spin waves. This state seems to be a good description for the quantum Hall skyrmion.
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photoluminescence spectrum of an interacting two dimensional Electron Gas at ν 1
Physical Review B, 2005Co-Authors: R. L. Doretto, Amir Ordacgi CaldeiraAbstract:We report on the theoretical photoluminescence spectrum of an interacting Two-Dimensional Electron Gas at filling factor one $(\ensuremath{\nu}=1)$. We considered a model similar to the one adopted to study the x-ray spectra of metals and solved it analytically using the bosonization method previously developed for the Two-Dimensional Electron Gas at $\ensuremath{\nu}=1$. We calculated the emission spectra of the right and the left circularly polarized radiations for the situations where the distance between the Two-Dimensional Electron Gas and the valence band hole is smaller and greater than the magnetic length. For the former, we showed that the polarized photoluminescence spectra can be understood as the recombination of the so-called excitonic state with the valence band hole whereas, for the latter, the observed emission spectra can be related to the recombination of a state formed by a spin down Electron bound to $n$ spin waves. This state seems to be a good description for the quantum Hall skyrmion.
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Photoluminescence spectrum of the interacting Two-Dimensional Electron Gas at \nu=1
2004Co-Authors: R. L. Doretto, Amir Ordacgi CaldeiraAbstract:We report on the theoretical photoluminescence spectrum of the interacting Two-Dimensional Electron Gas at filling factor one (\nu=1). We considered a model similar to the one adopted to study the X-ray spectra of metals and solved it analytically using the bosonization method previously developed for the Two-Dimensional Electron Gas at \nu=1. We calculated the emission spectra of the right and the left circularly polarized radiations for the situations where the distance between the Two-Dimensional Electron Gas and the valence band hole are smaller and greater than the magnetic length. For the former, we showed that the polarized photoluminescence spectra can be understood as the recombination of the so-called excitonic state with the valence band hole whereas, for the latter, the observed emission spectra can be related to the recombination of a state formed by a spin down Electron bound to n spin waves. This state seems to be a good description for the quantum Hall skyrmion.
L. N. Pfeiffer - One of the best experts on this subject based on the ideXlab platform.
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Current-induced nuclear-spin activation in a Two-Dimensional Electron Gas
Physical Review B: Condensed Matter and Materials Physics, 2009Co-Authors: C. R. Dean, B. A. Piot, G. Gervais, L. N. Pfeiffer, K. W. WestAbstract:Electrically detected nuclear magnetic resonance was studied in detail in a Two-Dimensional Electron Gas as a function of current bias and temperature. We show that applying a relatively modest dc-current bias, I_dc ~ 0.5 microAmps, can induce a re-entrant and even enhanced nuclear spin signal compared with the signal obtained under similar thermal equilibrium conditions at zero current bias. Our observations suggest that dynamic nuclear spin polarization by small current flow is possible in a Two-Dimensional Electron Gas, allowing for easy manipulation of the nuclear spin by simple switching of a dc current.
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Current-induced nuclear-spin activation in a Two-Dimensional Electron Gas
Physical Review B, 2009Co-Authors: Cory Dean, B. A. Piot, G. Gervais, L. N. Pfeiffer, K. W. WestAbstract:Electrically detected nuclear magnetic resonance was studied in detail in a Two-Dimensional Electron Gas as a function of current bias and temperature. We show that applying a relatively modest dc-current bias ${I}_{\text{dc}}\ensuremath{\simeq}0.5\text{ }\ensuremath{\mu}\text{A}$ can induce an enhanced nuclear-spin signal compared with the signal obtained under similar thermal equilibrium conditions at zero current bias. Our observations suggest that dynamic nuclear-spin polarization by small current flow is possible in a Two-Dimensional Electron Gas, allowing for easy manipulation of the nuclear spin by simple switching of a dc current.
G. Gervais - One of the best experts on this subject based on the ideXlab platform.
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Current-induced nuclear-spin activation in a Two-Dimensional Electron Gas
Physical Review B: Condensed Matter and Materials Physics, 2009Co-Authors: C. R. Dean, B. A. Piot, G. Gervais, L. N. Pfeiffer, K. W. WestAbstract:Electrically detected nuclear magnetic resonance was studied in detail in a Two-Dimensional Electron Gas as a function of current bias and temperature. We show that applying a relatively modest dc-current bias, I_dc ~ 0.5 microAmps, can induce a re-entrant and even enhanced nuclear spin signal compared with the signal obtained under similar thermal equilibrium conditions at zero current bias. Our observations suggest that dynamic nuclear spin polarization by small current flow is possible in a Two-Dimensional Electron Gas, allowing for easy manipulation of the nuclear spin by simple switching of a dc current.
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Current-induced nuclear-spin activation in a Two-Dimensional Electron Gas
Physical Review B, 2009Co-Authors: Cory Dean, B. A. Piot, G. Gervais, L. N. Pfeiffer, K. W. WestAbstract:Electrically detected nuclear magnetic resonance was studied in detail in a Two-Dimensional Electron Gas as a function of current bias and temperature. We show that applying a relatively modest dc-current bias ${I}_{\text{dc}}\ensuremath{\simeq}0.5\text{ }\ensuremath{\mu}\text{A}$ can induce an enhanced nuclear-spin signal compared with the signal obtained under similar thermal equilibrium conditions at zero current bias. Our observations suggest that dynamic nuclear-spin polarization by small current flow is possible in a Two-Dimensional Electron Gas, allowing for easy manipulation of the nuclear spin by simple switching of a dc current.
