We measure microwave frequency (4-40 GHz) photoresistance at low magnetic field B, in high mobility 2D electron gas samples, excited by signals applied to a transmission line fabricated on the sample surface. Oscillatory photoresistance vs B is observed. For excitation at the cyclotron resonance frequency, we find an unprecedented, giant relative photoresistance (\Delta R)/R of up to 250 percent. The photoresistance is apparently proportional to the square root of applied power, and disappears as the temperature is increased.Comment: 4 pages, 3 figure
We report resistivity measurements from 0.03 to 10 K in a dilute high mobility 2D electron system. Using an undoped GaAs/AlGaAs heterojunction in a gated field-effect transistor geometry, a wide range of densities, 0.16 x 10(10) to 7.5 x 10(10) cm(-2), are explored. For high densities, the results are quantitatively shown to be due to scattering by acoustic phonons and impurities. In an intermediate range of densities, a peak in the resistivity is observed for temperatures below 1 K. This nonmonotonic resistivity can be understood by considering the known scattering mechanisms of phonons, bulk, and interface ionized impurities. Still lower densities appear insulating to the lowest temperature measured.
Articles you may be interested inInelastic electron and Raman scattering from the collective excitations in quantum wires: Zero magnetic field AIP Advances 3, 042103 (2013); 10.1063/1.4800685 Counting statistics in an InAs nanowire quantum dot with a vertically coupled charge detector Appl. Phys. Lett. 100, 072110 (2012); 10.1063/1.3687198Linear and nonlinear conductance of ballistic quantum wires with hybrid confinementWe study the transport in a system of coupled quantum wires and show evidence for a resonant interaction that occurs whenever one of them is biased close to pinch off. Measuring the conductance of one of the wires, as the width of the other is varied, we observe a resonant peak in the conductance that is correlated to the point at which the other wire pinches off. The origin of this interaction remains undetermined at present, although its characteristics appear consistent with predictions that a correlated many-body state should form in narrow wires as their conductance vanishes.
The metallic conductivity of dilute two-dimensional holes in a GaAs HIGFET (Heterojunction Insulated-Gate Field-Effect Transistor) with extremely high mobility and large rs is found to have a linear dependence on temperature, consistent with the theory of interaction corrections in the ballistic regime. Phonon scattering contributions are negligible in the temperature range of our interest, allowing comparison between our measured data and theory without any phonon subtraction. The magnitude of the Fermi liquid interaction parameter F σ 0 determined from the experiment, however, decreases with increasing rs for rs > ∼ 22, a behavior unexpected from existing theoretical calculations valid for small rs.PACS numbers: 71.30.+h,73.40.Kp In two-dimensional (2D) charge carrier systems, it is well known that any amount of disorder in the absence of interactions between the carriers will localize the carriers, leading to an insulator with zero conductivity (σ) as the temperature (T ) is decreased to zero 1 . Recent experiments on high mobility dilute 2D systems, on the other hand, have shown a "metallic" behavior at low T , characterized by an increasing σ with decreasing T , and an apparent metal-insulator transition (MIT) as the carrier density is lowered 2 . There are three important energy scales in these systems. The first two are the Fermi energy and the interaction energy. Their ratio, which is r s , is around 10 or higher for the systems where the MIT is observed, implying that interaction must be playing a role. The other energy scale is related to the disorder in the system given byh/τ , where τ is the elastic scattering time. It has been found from more recent experiments that disorder is also playing a significant role. In particular, the critical density (n c for electrons and p c for holes), above which a system shows the metallic behavior, is found to decrease when disorder in the 2D system is decreased3 .An important question is whether this apparent metallic state is truly a new ground state of the 2D charge carriers or simply a novel finite temperature behavior of the 2D gas, since all experiments are done at finite T . What is measured in such experiment is the temperature coefficient, dσ/dT . The metallic behavior evinced by the observation of negative dσ/dT at finite T does not necessarily mean, however, a true metal with nonzero conductivity at T = 0. Recently, Zala et al.4 calculated the Fermi liquid interaction corrections to the conductivity in the asymptotic low temperature regime (T /T F ≪ 1 where T F is the Fermi temperature), and pointed out that the metallic behavior seen in the high mobility samples could be understood by taking into account of interaction corrections in the "high temperature" ballistic regime (k B T ≫h/τ ). They found that the conductivity of interacting 2D carriers changes linearly with T in the ballistic regime, T F ≫ T ≫h/k B τ , with the sign as well as the magnitude of dσ/dT depending on the strength of the interaction, while in the low temperature diffusive regime...
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