Anisotropic Corbino magnetothermopower in a quantum Hall system

Zalinge, van H Harm; Heijden, van der Rw Rob

doi:10.1103/physrevb.67.165311

Cited by 10 publications

(24 citation statements)

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“…In a two-dimensional electron gas (2DEG) embedded in a GaAs/AlGaAs heterostructure, however, it is well known that the latter dominates the measured thermopower, 5, 6 unless measurements are done at very low temperatures 150 mK; 4, 11 in standard measurements using an external heater to introduce the temperature gradient ∇T , the resulting heat current is predominantly carried by the phonons in the host crystal, leading to the dominance of the phonon-drag contribution despite the weakness of the electron-phonon interaction. The measurement of Corbino thermopower in QH systems at 1.5 K was previously reported by Zalinge et al 6 They used a laser spot as a heater to introduce ∇T , and therefore the measured thermovoltages were primarily attributed to the phonon-drag.The diffusion contribution can be selectively measured by introducing the gradient only to the electron temperature T e , leaving the lattice temperature T L intact. This can be achieved by directly passing a moderately large current to a section of 2DEG designated to serve as a heater.…”

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Diffusion Thermopower of Quantum Hall States Measured in Corbino Geometry

2013

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We have measured the diffusion thermopower of a quantum Hall system in a Corbino setup. A concentric electrontemperature gradient is introduced by irradiating microwaves, via a coplanar waveguide, near the outer rim of a circular mesa of a two-dimensional electron gas. The resulting radial thermovoltages exhibit sawtooth-like oscillations with the magnetic field, taking large positive (negative) values just below (above) integer fillings with sign reversal at the center of the quantum Hall plateaus. The behavior is in agreement with a recent theory [Y. Barlas and K. Yang: Phys. Rev. B 85 (2012) 195107], which treats disorder within the self-consistent Born approximation.KEYWORDS: diffusion thermopower, quantum Hall effect, Corbino disk, microwave heating, coplanar waveguide, conductivity, two-dimensional electron gasThe thermopower of quantum Hall (QH) systems has been attracting interest as a sensitive probe to examine the electronic properties of the systems, 1-8 which is further spurred by a recent proposal of the possibility to explore intriguing statistics of the quasiparticles in the ν = 5/2 fractional QH state. [9][10][11][12] The vast majority of the measurements have been performed in the Hall bar geometry thus far (see, e.g., ref.5 and references therein). As will be detailed below, the radial thermopower S rr measured in the Corbino geometry is qualitatively different from the longitudinal thermopower S xx measured in the Hall bar geometry.6, 10 The purpose of the present paper is to report our measurements of the diffusion thermopower in the Corbino geometry for integer QH states.The thermopower generally contains contributions from two distinct mechanisms: diffusion and phonon drag. 5 The high sensitivity to the electronic properties is expected for the former contribution. In a two-dimensional electron gas (2DEG) embedded in a GaAs/AlGaAs heterostructure, however, it is well known that the latter dominates the measured thermopower, 5, 6 unless measurements are done at very low temperatures 150 mK; 4, 11 in standard measurements using an external heater to introduce the temperature gradient ∇T , the resulting heat current is predominantly carried by the phonons in the host crystal, leading to the dominance of the phonon-drag contribution despite the weakness of the electron-phonon interaction. The measurement of Corbino thermopower in QH systems at 1.5 K was previously reported by Zalinge et al. 6 They used a laser spot as a heater to introduce ∇T , and therefore the measured thermovoltages were primarily attributed to the phonon-drag.The diffusion contribution can be selectively measured by introducing the gradient only to the electron temperature T e , leaving the lattice temperature T L intact. This can be achieved by directly passing a moderately large current to a section of 2DEG designated to serve as a heater.13, 14 It will be practically very difficult, however, to apply this Joule heating technique to a Corbino device, since it requires the heating current to pass only along the outer (or ...

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“…6,10 We start with the transport equation that relates the current density j to the applied electric field E and the temperature gradient ∇T ,…”

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Diffusion Thermopower of Quantum Hall States Measured in Corbino Geometry

2013

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“…Early thermopower experiments in Corbino geometry have failed to observe the expected sign-changing behavior [14]. It has been reported, however, in other experimental works using the Corbino geometry [15].…”

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confidence: 95%

Thermoelectricity in Quantum Hall Corbino Structures

et al. 2020

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We measure the thermoelectric response of Corbino structures in the quantum Hall effect regime and compare it with a theoretical analysis. The measured thermoelectric voltages are qualitatively and quantitatively simulated based upon the independent measurement of the conductivity, indicating that they originate predominantly from the electron diffusion. In contrast to earlier Hall-bar experiments, electronphonon interaction does not lead to a phonon-drag contribution. This implies a description of the Onsager coefficients on the basis of a single transmission function, from which both thermovoltage and conductivity can be predicted with a single fitting parameter. Furthermore, it lets us predict a figure of merit for the efficiency of thermoelectric cooling, which becomes very large for partially filled Landau levels and high magnetic fields.

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“…We leave this problem for further study. The influence of anisotropy on thermopower in Corbino geometry has been already detected experimentally [28] but was not studied systematically. We note that application of MW irradiation allows us to study the region of relatively weak magnetic fields, whereas the previous measurements of thermopower in Corbino geometry [28,30] demonstrated peculiarities of thermoelectric response only in the quantum Hall regime.…”

Section: Theory and Discussionmentioning

confidence: 99%

Magnetocapacitance oscillations and thermoelectric effect in a two-dimensional electron gas irradiated by microwaves

Levin

Gusev

Raichev³

et al. 2016

Phys. Rev. B

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To study the influence of microwave irradiation on two-dimensional electrons, we apply a method based on capacitance measurements in GaAs quantum well samples where the gate covers a central part of the layer. We find that the capacitance oscillations at high magnetic fields, caused by the oscillations of thermodynamic density of states, are not essentially modified by microwaves. However, in the region of fields below 1 Tesla, we observe another set of oscillation, with the period and the phase identical to those of microwave induced resistance oscillations. The phenomenon of microwave induced capacitance oscillations is explained in terms of violation of the Einstein relation between conductivity and the diffusion coefficient in the presence of microwaves, which leads to a dependence of the capacitor charging on the anomalous conductivity. We also observe microwaveinduced oscillations in the capacitive response to periodic variations of external heating. These oscillations appear due to the thermoelectric effect and are in antiphase with microwave induced resistance oscillations because of the Corbino-like geometry of our experimental setup.

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Anisotropic Corbino magnetothermopower in a quantum Hall system

Cited by 10 publications

References 24 publications

Diffusion Thermopower of Quantum Hall States Measured in Corbino Geometry

Diffusion Thermopower of Quantum Hall States Measured in Corbino Geometry

Thermoelectricity in Quantum Hall Corbino Structures

Magnetocapacitance oscillations and thermoelectric effect in a two-dimensional electron gas irradiated by microwaves

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