Measurement of diffusion thermopower in the quantum Hall systems

Fujita, Kazuhiro; Endo, Akira; Katsumoto, Shingo; Iye, Yasuhiro

doi:10.1016/j.physe.2009.10.032

Cited by 12 publications

(21 citation statements)

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“…Fujita et al [6] measured the 2DEG's contribution to these effects using the direct Joule heating of the 2DEG at a low temperature (∼0.04 K). They experimentally suggested that this Joule heating method raises only the electron temperature.…”

Section: Introductionmentioning

confidence: 99%

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Temperature distribution in nano-devices under a strong magnetic field

Hirayama

Endo

Fujita

et al. 2011

Computer Physics Communications

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Section: Introductionmentioning

confidence: 99%

“…The schematic diagram of the experimental system [6], including the Joule heating part, and the observed Nernst coefficient V yx by the method are shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

Temperature distribution in nano-devices under a strong magnetic field

Hirayama

Endo

Fujita

et al. 2011

Computer Physics Communications

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“…Fujita et al 6 observed the Nernst voltage of a two-dimensional electron gas (2DEG) using the direct Joule heating method, by which they could accurately extract the electron behavior without the influence of phonon drag, at low temperature (40 mK). They found that an unusual Nernst voltage which is not theoretically expected appears under a strong magnetic field, B > 1.8 T. In a previous study, 7 we simulated the distributions of the temperature T and the voltage / of a 2DEG.…”

Section: Introductionmentioning

confidence: 99%

“…6 The cooling of the system is a complicated process, since it may be related to several thermoelectric and thermomagnetic phenomena. To clarify the mechanism of the cooling effect, we here numerically analyze the contributions of various effects.…”

Section: Introductionmentioning

confidence: 99%

Temperature Distribution in Two-Dimensional Electron Gases under a Strong Magnetic Field

Hirayama

Endo

Fujita

et al. 2010

Journal of Elec Materi

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Two-dimensional electron gases having an electrochemical potential gradient under a magnetic field are numerically examined using the finite-difference method. The temperature, voltage, electric current, and heat flux are calculated from transport equations describing thermoelectric and thermomagnetic effects, namely the Hall, Nernst, Ettingshausen, and Righi-Leduc effects. The results show that a magnetic field distorts equipotential lines and generates an uneven temperature distribution. In particular, a part of the system is found to become colder than the temperature of the heat baths. The cooling effect under a strong magnetic field is due primarily to the Ettingshausen and Hall effects.

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“…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 inner) rim of the annularly patterned 2DEG. In the present study, we take an alternative approach, microwave irradiation, for the electron heating.…”

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confidence: 99%

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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Measurement of diffusion thermopower in the quantum Hall systems

Cited by 12 publications

References 12 publications

Temperature distribution in nano-devices under a strong magnetic field

Temperature distribution in nano-devices under a strong magnetic field

Temperature Distribution in Two-Dimensional Electron Gases under a Strong Magnetic Field

Diffusion Thermopower of Quantum Hall States Measured in Corbino Geometry

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