The effect of carrier density gradients on magnetotransport data measured in Hall bar geometry

Пономаренко, Л. А.; Lang, D.T.N. de; Visser, A. de; Kulbachinskii, V. A.; Галиев, Г. Б.; Künzel, H.; Pruisken, A. M. M.

doi:10.1016/j.ssc.2004.02.021

Cited by 15 publications

(12 citation statements)

References 12 publications

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“…2 has been observed before in large, macroscopic, Hall-bar shaped samples, and has been attributed to the existence of a longitudinal densitygradient in the samples [12]. Recently, Ponomarenko et al and Karmakar et al [13] reported on the observation of this symmetry and suggested a model that details how the symmetry originates from a density gradient. Due to a longitudinal density-gradient in their samples the 'left' and 'right' Hall resistances of the samples are not equal, R l H = R r H , and are instead found to be B-shifted with respect to each other.…”

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confidence: 64%

Symmetries of the resistance of mesoscopic samples in the quantum Hall regime

et al. 2004

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The symmetry properties of the resistance of mesoscopic samples in the quantum Hall regime are investigated. In addition to the reciprocity relation, our samples obey new symmetries, that relate resistances measured with different contact configurations. Different kinds of symmetries are identified, depending on whether the magnetic field value is such that the system is above, or below, a quantum Hall transition. Related symmetries have recently been reported for macroscopic samples in the quantum Hall regime by Ponomarenko et al. (Solid State Commun. 130, 705 (2004)), and Karmakar et al. (Preprint cond-mat/0309694).

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confidence: 64%

Symmetries of the resistance of mesoscopic samples in the quantum Hall regime

et al. 2004

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“…Most of the studies on these aspects are on 2D semiconductor devices (see for instance Ref. 30 and reference therein), while little discussion is dedicated to graphene. In graphene, it is common practice 20,22 to perform a symmetrization of the data with respect to magnetic field.…”

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confidence: 99%

“…This variation leads to a charge density gradient in the graphene layer, which is known to affect the experimental data curves. 30 For linear density variations in the longitudinal direction, the best resistance estimate is obtained by averaging the values measured at opposite sides of the device. 31 The residual small tilt in the data of Fig.…”

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confidence: 99%

Tuning of quantum interference in top-gated graphene on SiC

et al. 2013

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We report on quantum-interference measurements in top-gated Hall bars of monolayer graphene epitaxially grown on the Si face of SiC, in which the transition from negative to positive magnetoresistance was achieved varying temperature and charge density. We perform a systematic study of the quantum corrections to the magnetoresistance due to quantum interference of quasiparticles and electron-electron interaction. We analyze the contribution of the different scattering mechanisms affecting the magnetotransport in the −2.0 × 10 10 cm −2 to 3.75 × 10 11 cm −2 density region and find a significant influence of the charge density on the intravalley scattering time. Furthermore, we observe a modulation of the electron-electron interaction with charge density not accounted for by present theory. Our results clarify the role of quantum transport in SiC-based devices, which will be relevant in the development of a graphene-based technology for coherent electronics.

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“…18 When such a gradient exists, it induces a directional change in the HE and thus it contributes to a change in the voltage drop measured between two points on the same side of the current path. Therefore, the antisymmetric contribution behaves as the difference between the HE signals with different carrier densities.…”

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Antisymmetric magnetoresistance of theSrTiO3/LaAlO3interface

Seri

Klein

2009

Phys. Rev. B

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The longitudinal resistance R xx of the SrTiO 3 / LaAlO 3 interface with magnetic fields applied perpendicular to the interface has an antisymmetric term ͓namely, R xx ͑H͒ R xx ͑−H͔͒ which increases with decreasing temperature and increasing field. We argue that the origin of this phenomenon is a nonhomogeneous Hall effect with clear contribution of an extraordinary Hall effect, suggesting the presence of nonuniform field-induced magnetization.The quasi-two-dimensional electron gas ͑q2DEG͒ that forms at the interface between the two insulating oxides, SrTiO 3 ͑STO͒ and LaAlO 3 ͑LAO͒, has fascinated many researchers who have been trying to elucidate the properties of this system. 1-9 Nevertheless, some of the most basic properties of this material are still controversial. Thus, contrary to the apparent consensus concerning the superconducting ground state of this system below 300 mK which obeys the Kosterlitz-Thouless phase transition, 3,10 the existence and nature of the magnetism are still open questions. While there is a theoretical prediction for a magnetic order, 11 the experimental situation is more complicated where some groups reported hysteretic magnetoresistance ͑MR͒ which suggests ferromagnetic order 12 and other reported lack of hysteresis but unusual magnetoresistance behavior which they attributed to some kind of magnetic order. 13 Here, we present data showing that the MR of the LAO/ STO interface with magnetic fields applied perpendicular to the interface has an antisymmetric term which increases with decreasing temperature and increasing field. While the qualitative behavior is common to all the patterns we have studied, the magnitude and the sign of the phenomenon vary considerably even between neighboring segments of the same pattern. Based on field, temperature, and angular dependent measurements of the Hall effect ͑HE͒ and the MR, we argue that the likely source of this phenomenon is a nonhomogeneous HE with a clear contribution of a nonuniform extraordinary Hall effect ͑EHE͒. 14 This interpretation implies that the applied magnetic field induces nonuniform magnetization. The nonuniform field-induced magnetization may suggest that either the induced magnetization is extrinsic to the q2DEG or that other nonuniformity affects locally the electron gas magnetization. The induced magnetization is likely to be the source of the observed large positive and negative MRs when magnetic fields are applied perpendicular and parallel to the interface, respectively. The negative MR is in the form of sharp and narrow dips, indicating strong magnetic anisotropy.While we do not resolve the elusive issue of magnetism in LAO/STO interfaces, we present multiple pieces of evidence for nonuniform field-induced magnetization at low temperatures which provide central ingredients for elucidating the nature of the q2DEG. The evidence for sizable EHE which we use for detecting the magnetism is of importance by itself for exploring the transport mechanism in this system and in addition it opens the door for future spintr...

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The effect of carrier density gradients on magnetotransport data measured in Hall bar geometry

Cited by 15 publications

References 12 publications

Symmetries of the resistance of mesoscopic samples in the quantum Hall regime

Symmetries of the resistance of mesoscopic samples in the quantum Hall regime

Tuning of quantum interference in top-gated graphene on SiC

Antisymmetric magnetoresistance of theSrTiO3/LaAlO3interface

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