85 research outputs found

    Spin Polarization of Two-Dimensional Electrons Determined from Shubnikov-de Haas Oscillations as a Function of Angle

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    Recent experiments in the two dimensional electron systems in silicon MOSFETs have shown that the in-plane magnetic field HsatH_{sat} required to saturate the conductivity to its high-field value and the magnetic field HsH_s needed to completely align the spins of the electrons are comparable. By small-angle Shubnikov-de Haas oscillation measurements that allow separate determinations of the spin-up and spin-down subband populations, we show that Hsat=HsH_{sat}=H_s to an accuracy of 5% for electron densities ns>3Γ—1011n_s > 3 \times 10^{11} cmβˆ’2^{-2}.Comment: 4 pages, 3 figures; minor changes, references updated and adde

    Spin polarization of strongly interacting 2D electrons: the role of disorder

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    In high-mobility silicon MOSFET's, the gβˆ—mβˆ—g^*m^* inferred indirectly from magnetoconductance and magnetoresistance measurements with the assumption that gβˆ—ΞΌBHs=2EFg^*\mu_BH_s=2E_F are in surprisingly good agreement with gβˆ—mβˆ—g^*m^* obtained by direct measurement of Shubnikov-de Haas oscillations. The enhanced susceptibility Ο‡βˆ—βˆ(gβˆ—mβˆ—)\chi^* \propto (g^*m^*) exhibits critical behavior of the form Ο‡βˆ—βˆ(nβˆ’n0)βˆ’Ξ±\chi^* \propto (n - n_0)^{-\alpha}. We examine the significance of the field scale HsH_s derived from transport measurements, and show that this field signals the onset of full spin polarization only in the absence of disorder. Our results suggest that disorder becomes increasingly important as the electron density is reduced toward the transition.Comment: 4 pages, 3 figure

    In-plane Magnetoconductivity of Si-MOSFET's: A Quantitative Comparison between Theory and Experiment

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    For densities above n=1.6Γ—1011n=1.6 \times 10^{11} cmβˆ’2^{-2} in the strongly interacting system of electrons in two-dimensional silicon inversion layers, excellent agreement between experiment and the theory of Zala, Narozhny and Aleiner is obtained for the response of the conductivity to a magnetic field applied parallel to the plane of the electrons. However, the Fermi liquid parameter F0Οƒ(n)F_0^\sigma(n) and the valley splitting Ξ”V(n)\Delta_V(n) obtained from fits to the magnetoconductivity, although providing qualitatively correct behavior (including sign), do not yield quantitative agreement with the temperature dependence of the conductivity in zero magnetic field. Our results suggest the existence of additional scattering processes not included in the theory in its present form

    Conductivity of Silicon Inversion Layers: comparison with and without in-plane magnetic field

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    A detailed comparison is presented of the temperature dependence of the conductivity of dilute, strongly interacting electrons in two-dimensional silicon inversion layers in the metallic regime in the presence and in the absence of a magnetic field. We show explicitly and quantitatively that a magnetic field applied parallel to the plane of the electrons reduces the slope of the conductivity versus temperature curves to near zero over a broad range of electron densities extending from ncn_c to deep in the metallic regime where the high field conductivity is on the order of 10e2/h10 e^2/h. The strong suppression (or "quenching") of the metallic behavior by a magnetic field sets an important constraint on theory.Comment: 4 pages, 4 figure

    Effect of parallel magnetic field on the Zero Differential Resistance State

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    The non-linear zero-differential resistance state (ZDRS) that occurs for highly mobile two-dimensional electron systems in response to a dc bias in the presence of a strong magnetic field applied perpendicular to the electron plane is suppressed and disappears gradually as the magnetic field is tilted away from the perpendicular at fixed filling factor Ξ½\nu. Good agreement is found with a model that considers the effect of the Zeeman splitting of Landau levels enhanced by the in-plane component of the magnetic field.Comment: 4 pages, 4 figure
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