Resonant Phonon Scattering in Quantum Hall Systems Driven by dc Electric Fields

Zhang, W.; Zudov, M. A.; Pfeiffer, L. N.; West, K. W.

doi:10.1103/physrevlett.100.036805

Phys. Rev. Lett.

2008

DOI: 10.1103/physrevlett.100.036805

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Resonant Phonon Scattering in Quantum Hall Systems Driven by dc Electric Fields

W. Zhang

M. A. Zudov

L. N. Pfeiffer³

et al.

Abstract: Using dc excitation to spatially tilt Landau levels, we study resonant acoustic phonon scattering in two-dimensional electron systems. We observe that dc electric field strongly modifies phonon resonances, transforming resistance maxima into minima and back into maxima. Further, phonon resonances are enhanced dramatically in the nonlinear dc response and can be detected even at low temperatures. Most of our observations can be explained in terms of dc-induced (de)tuning of the resonant acoustic phonon scatteri… Show more

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Cited by 85 publications

(104 citation statements)

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“…6,7 The period of phonon-induced oscillations is tunable by an additional dc electric field. 8,9 Also a new type of QHE was enabled in high mobility 2DEGs, the re-entrant integer quantum Hall effect (RIQHE). 10,11 In the regime of the RIQHE the longitudinal resistance between integer filling factors decreases to zero suggesting fractional filling factors, but the corresponding Hall plateaus are quantized at integer values.…”

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Magnetoresistance in a high-mobility two-dimensional electron gas

et al. 2011

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In a high-mobility two-dimensional electron gas (2DEG) in a GaAs/Al 0.3 Ga 0.7 As quantum well we observe a strong magnetoresistance. In lowering the electron density, the magnetoresistance gets more pronounced and reaches values of more than 300%. We observe that the huge magnetoresistance vanishes when increasing the temperature. An additional density-dependent factor is introduced to be able to fit the parabolic magnetoresistance to the electron-electron interaction correction. Since the first observation of the fractional quantum Hall effect (FQHE) 1,2 the quality and the mobility of the two-dimensional electron gas (2DEG) increased by more than two orders of magnitude. The increased mobility has allowed not only the observation of the FQHE at many different filling factors and smaller magnetic fields but also many new effects. So, microwave-induced oscillations were observed, which were up to now not fully understood. [3][4][5] In weak magnetic fields the increased mobility enabled also the observation of phonon-induced resistance oscillations, which are caused by inelastic scattering between electrons and three-dimensional acoustic phonons. 6,7 The period of phonon-induced oscillations is tunable by an additional dc electric field. 8,9 Also a new type of QHE was enabled in high mobility 2DEGs, the re-entrant integer quantum Hall effect (RIQHE). 10,11 In the regime of the RIQHE the longitudinal resistance between integer filling factors decreases to zero suggesting fractional filling factors, but the corresponding Hall plateaus are quantized at integer values.Here we will present the observation of a huge magnetoresistance in a high mobility 2DEG which depends strongly on electron density and temperature.Our samples were cleaved from a wafer of a high-mobility GaAs/Al 0.3 Ga 0.7 As quantum well grown by molecular-beam epitaxy. The quantum well has a width of 30 nm and is Si-doped from both sides. The 2DEG is located 150 nm beneath the surface and has an electron density of n e ≈ 3.1 × 10 11 cm −2 and a mobility of μ ≈ 11.9 × 10 6 cm 2 /Vs in the dark. The specimens are Hall bars with a total length of 1.2 μm, a width of w = 200 μm and a potential probe spacing of l = 275 μm [see Fig. 1(a)]. The Hall bars were defined by photolithography and wet etching. Different ungated and gated samples were used for the magnetotransport measurements. In the case of the gated sample there is an additional layer of 600 nm PMMA between the Hall bar and the metallic top-gate to avoid leakage current. We apply top-gate voltages up to −6 V to manipulate the electron density. Our measurements were performed in a dilution refrigerator with a base temperature of 20 mK. The measurements were carried out by using low-frequency (13 Hz) lock-in technique.Figure 1(a) shows the longitudinal resistance R xx and the Hall resistance R xy vs. magnetic field B to demonstrate the quality of our samples. A series of different fractional quantum Hall states appears for filling factor ν < 2. We observe also the filling factor ν = 5/2. Over the ...

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Magnetoresistance in a high-mobility two-dimensional electron gas

et al. 2011

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“…Therefore, in the presence of microwaves and strong dc electric field the resistivity is explained by the "displacement" mechanism, i. e. in terms of combined inter-Landau level transitions which are composed of both microwave absorption and impurity scattering. Somewhat similar effect of dc electric field on resonant acoustic phonon scattering [21] was recently observed [8].In this Letter, we study the effect of dc electric field on microwave photoresistivity near cyclotron resonance subharmonics of a high mobility 2DES. Surprisingly, the nonlinear response around the second cyclotron resonance subharmonic, ǫ ac = 1/2, closely mimics the response near cyclotron resonance, ǫ ac = 1, despite a factor of two difference in magnetic fields.…”

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confidence: 99%

“…Another notable effect is Hall field-induced resistance oscillations (HIRO) emerging under strong dc electric field [4,5]. Recently, it was demonstrated that dc field also induces strong resistance suppression [5,6] and zero-differential resistance states [7,8].Stepping from the inter-Landau level transitions due to microwave absorption and/or impurity scattering, MIRO and HIRO are controlled by simple parameters, ǫ ac ≡ ω/ω C and ǫ dc ≡ eE(2R C )/ ω C , respectively. Here, ω = 2πf is the microwave frequency, ω C = eB/m * is the cyclotron frequency, E is the Hall electric field, and 2R C is the cyclotron diameter.…”

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Microwave Photoresistance in dc-Driven 2D Systems at Cyclotron Resonance Subharmonics

et al. 2008

Phys. Rev. Lett.

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We study microwave photoresistivity oscillations in a high mobility two-dimensional electron system subject to strong dc electric fields. We find that near the second subharmonic of the cyclotron resonance the frequency of the resistivity oscillations with dc electric field is twice the frequency of the oscillations at the cyclotron resonance, its harmonics, or in the absence of microwave radiation. This observation is discussed in terms of the microwave-induced sidebands in the density of states and the interplay between different scattering processes in the separated Landau level regime. Over the recent years many remarkable phenomena, other than conventional Shubnikov-de Haas oscillations [1], have been discovered in high Landau levels of two-dimensional electron systems (2DES). A lot of attention has been paid to microwave-induced resistance oscillations (MIRO) [2] and zero-resistance states [3] formed at the MIRO minima. Another notable effect is Hall field-induced resistance oscillations (HIRO) emerging under strong dc electric field [4,5]. Recently, it was demonstrated that dc field also induces strong resistance suppression [5,6] and zero-differential resistance states [7,8].Stepping from the inter-Landau level transitions due to microwave absorption and/or impurity scattering, MIRO and HIRO are controlled by simple parameters, ǫ ac ≡ ω/ω C and ǫ dc ≡ eE(2R C )/ ω C , respectively. Here, ω = 2πf is the microwave frequency, ω C = eB/m * is the cyclotron frequency, E is the Hall electric field, and 2R C is the cyclotron diameter. MIRO maxima + and minima − are found at ǫ ± ac ≃ n ∓ φ ac , φ ac ≤ 1/4 (n ∈ Z + ) [9, 10], while HIRO maxima (minima) occur near integer (half-integer) values of ǫ dc [14]. To explain MIRO, "displacement" [11] and "inelastic" [12] models have been proposed. Until recently it was believed that the "inelastic" mechanism, originating from the oscillatory correction to the electron distribution, dominates over the "displacement" mechanism, which is based on microwave-assisted scattering off of impurities. However, recent experiments [13] have shown that the "displacement" mechanism cannot be ignored.Remarkably, in addition to MIRO at integer ǫ ac , many experiments [9,15] reported similar features near certain fractional values of ǫ ac = 1/2, 3/2, 5/2, 1/3, 2/3. These oscillations were initially explained by a multiphoton "displacement" mechanism [16] which relies on a single electron simultaneously absorbing multiple photons. However, recently [17] it was argued that in the regime of separated Landau levels "inelastic" multiphoton mechanism dominates the response while at the crossover from separated to overlapped Landau levels, two single-photon "inelastic" mechanisms become important. The first of these mechanisms is based on a resonant series of consecutive single-photon transitions [18]. The other originates from microwave-induced sidebands in the density of states of the disorder-broadened Landau levels [17].When a 2DES is subject to microwaves and a strong dc electric field si...

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“…Recently, the oscillatory behavior in the nonlinear magnetotransport has attracted much attention: in a 2D system even without irradiation, a relatively weak current can induce drastic suppression and strong oscillations of the differential magnetoresistance, and may result in a state of zero-differential resistance. 22,23,24,25,26 Several theoretical models have been proposed in an attempt to explain this interesting nonlinear phenomenon. 27,28,29,30 Numerical examinations based on the current-control transport scheme were shown in good agreement with the experimental observation for differential magnetoresistivity as a function of the ratio of the current density to the magnetic field in both the magnetic-field sweeping and the current-sweeping configurations covering both separated and overlapping Landau level regimes.…”

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Oscillatory nonlinear differential magnetoresistance of highly mobile 2D electrons in high Landau levels

Lei¹

2009

Physica E: Low-dimensional Systems and Nanostructures

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We examine the current-induced magnetoresistance oscillations in high-mobility two-dimensional electron systems using the balance-equation scheme for nonlinear magnetotransort. The reported analytical expressions for differential magnetoresistivity at high filling factors in the overlapping Landau-level regime, which show good agreement with the experimental observation and the numerical calculation, may be helpful in extracting physical information from experiments.In addition to the universally existing Shubnikov-de Haas oscillations (SdHO), many different kinds of magnetoresistance oscillations were discovered in the past few years in high-mobility two-dimensional (2D) electron systems (ES) subject to a weak perpendicular magnetic field and have become a field of great interest. These resistance oscillations always occur at low temperatures and are related to magnetotransport of 2D electrons occupying high Landau levels (LLs). Among them the microwave-induced magnetoresistance oscillations and the related zero-resistance states were the central focus of most experimental 1,2,3,4,5,6,7,8,9,10 and theoretical 11,12,13,14,15,16,17,18,19,20,21 studies. Recently, the oscillatory behavior in the nonlinear magnetotransport has attracted much attention: in a 2D system even without irradiation, a relatively weak current can induce drastic suppression and strong oscillations of the differential magnetoresistance, and may result in a state of zero-differential resistance. 22,23,24,25,26 Several theoretical models have been proposed in an attempt to explain this interesting nonlinear phenomenon. 27,28,29,30 Numerical examinations based on the current-control transport scheme were shown in good agreement with the experimental observation for differential magnetoresistivity as a function of the ratio of the current density to the magnetic field in both the magnetic-field sweeping and the current-sweeping configurations covering both separated and overlapping Landau level regimes. 27 It is reported recently that by a systematic analysis of current-induced magnetoresistance oscillations, important physical information about electron-electron interaction on the single particle life time can be extracted. 31 From the point of view of experiment, an analytical expression for differential magnetoresistivity, even applies only within limited ranges, is highly desirable because it can be of great help to extract important physical information from experimental data. So far, a reliable analytical expression derived from experimentally confirmed theoretical models is still lacking.We examine this issue based on the balance-equation scheme of nonlinear magnetotransport, 27 which deals with a 2D system consisting of N s electrons in a unit area of the x-y plane and subjected to a uniform magnetic field B = (0, 0, B) in the z direction. These electrons, scattered by randomly distributed impurities and by phonons in the lattice, perform an integrative drift motion under the influence of a uniform electric field E in the x-y plane. For h...

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Resonant Phonon Scattering in Quantum Hall Systems Driven by dc Electric Fields

Cited by 85 publications

References 39 publications

Magnetoresistance in a high-mobility two-dimensional electron gas

Magnetoresistance in a high-mobility two-dimensional electron gas

Microwave Photoresistance in dc-Driven 2D Systems at Cyclotron Resonance Subharmonics

Oscillatory nonlinear differential magnetoresistance of highly mobile 2D electrons in high Landau levels

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