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Hossain MS, Ma MK, Rosales KAV, Chung YJ, Pfeiffer LN, West KW, Baldwin KW, Shayegan M. Observation of spontaneous ferromagnetism in a two-dimensional electron system. Proc Natl Acad Sci U S A 2020; 117:32244-32250. [PMID: 33273119 PMCID: PMC7768770 DOI: 10.1073/pnas.2018248117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
What are the ground states of an interacting, low-density electron system? In the absence of disorder, it has long been expected that as the electron density is lowered, the exchange energy gained by aligning the electron spins should exceed the enhancement in the kinetic (Fermi) energy, leading to a (Bloch) ferromagnetic transition. At even lower densities, another transition to a (Wigner) solid, an ordered array of electrons, should occur. Experimental access to these regimes, however, has been limited because of the absence of a material platform that supports an electron system with very high quality (low disorder) and low density simultaneously. Here we explore the ground states of interacting electrons in an exceptionally clean, two-dimensional electron system confined to a modulation-doped AlAs quantum well. The large electron effective mass in this system allows us to reach very large values of the interaction parameter [Formula: see text], defined as the ratio of the Coulomb to Fermi energies. As we lower the electron density via gate bias, we find a sequence of phases, qualitatively consistent with the above scenario: a paramagnetic phase at large densities, a spontaneous transition to a ferromagnetic state when [Formula: see text] surpasses 35, and then a phase with strongly nonlinear current-voltage characteristics, suggestive of a pinned Wigner solid, when [Formula: see text] exceeds [Formula: see text] However, our sample makes a transition to an insulating state at [Formula: see text], preceding the onset of the spontaneous ferromagnetism, implying that besides interaction, the role of disorder must also be taken into account in understanding the different phases of a realistic dilute electron system.
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Affiliation(s)
- M S Hossain
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
| | - M K Ma
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
| | | | - Y J Chung
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
| | - L N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
| | - K W West
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
| | - K W Baldwin
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
| | - M Shayegan
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544
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2
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Movva HCP, Fallahazad B, Kim K, Larentis S, Taniguchi T, Watanabe K, Banerjee SK, Tutuc E. Density-Dependent Quantum Hall States and Zeeman Splitting in Monolayer and Bilayer WSe_{2}. PHYSICAL REVIEW LETTERS 2017; 118:247701. [PMID: 28665633 DOI: 10.1103/physrevlett.118.247701] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Indexed: 06/07/2023]
Abstract
We report a study of the quantum Hall states (QHS) of holes in mono- and bilayer WSe_{2}. The QHS sequence transitions between predominantly even and predominantly odd filling factors as the hole density is tuned in the range 1.6-12×10^{12} cm^{-2}. Measurements in tilted magnetic fields reveal an insensitivity of the QHS to the in-plane magnetic field, evincing that the hole spin is locked perpendicular to the WSe_{2} plane. Furthermore, the QHS sequence is insensitive to an applied electric field. These observations imply that the QHS sequence is controlled by the Zeeman-to-cyclotron energy ratio, which remains constant as a function of perpendicular magnetic field at a fixed carrier density, but changes as a function of density due to strong electron-electron interaction.
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Affiliation(s)
- Hema C P Movva
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
| | - Babak Fallahazad
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
| | - Kyounghwan Kim
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
| | - Stefano Larentis
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
| | - Takashi Taniguchi
- National Institute of Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- National Institute of Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305-0044, Japan
| | - Sanjay K Banerjee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
| | - Emanuel Tutuc
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
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3
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Taneja D, Shlimak I, Narayan V, Kaveh M, Farrer I, Ritchie D. Reappearance of linear hole transport in an ambipolar undoped GaAs/AlGaAs quantum well. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:185302. [PMID: 28266927 DOI: 10.1088/1361-648x/aa6529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report the results of an investigation of ambipolar transport in a quantum well of 15 nm width in an undoped GaAs/AlGaAs structure, which was populated either by electrons or holes using positive or negative gate voltage V tg, respectively. More attention was focussed on the low concentration of electrons n and holes p near the metal-insulator transition (MIT). It is shown that the electron mobility [Formula: see text] increases almost linearly with increase of n and is independent of temperature T in the interval 0.3 K-1.4 K, while the hole mobility [Formula: see text] depends non-monotonically on p and T. This difference is explained on the basis of the different effective masses of electrons and holes in GaAs. Intriguingly, we observe that at low p the source-drain current (I SD)-voltage (V) characteristics, which become non-linear beyond a certain I SD, exhibit a re-entrant linear regime at even higher I SD. We find, remarkably, that the departure and reappearance of linear behaviour are not due to non-linear response of the system, but due to an intrinsic mechanism by which there is a reduction in the net number of mobile carriers. This effect is interpreted as evidence of inhomogeneity of the conductive 2D layer in the vicinity of MIT and trapping of holes in 'dead ends' of insulating islands. Our results provide insights into transport mechanisms as well as the spatial structure of the 2D conducting medium near the 2D MIT.
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Affiliation(s)
- Deepyanti Taneja
- Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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4
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Renard VT, Piot BA, Waintal X, Fleury G, Cooper D, Niida Y, Tregurtha D, Fujiwara A, Hirayama Y, Takashina K. Valley polarization assisted spin polarization in two dimensions. Nat Commun 2015; 6:7230. [PMID: 26027889 PMCID: PMC4458877 DOI: 10.1038/ncomms8230] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 04/20/2015] [Indexed: 11/15/2022] Open
Abstract
Valleytronics is rapidly emerging as an exciting area of basic and applied research. In two-dimensional systems, valley polarization can dramatically modify physical properties through electron-electron interactions as demonstrated by such phenomena as the fractional quantum Hall effect and the metal-insulator transition. Here, we address the electrons' spin alignment in a magnetic field in silicon-on-insulator quantum wells under valley polarization. In stark contrast to expectations from a non-interacting model, we show experimentally that less magnetic field can be required to fully spin polarize a valley-polarized system than a valley-degenerate one. Furthermore, we show that these observations are quantitatively described by parameter-free ab initio quantum Monte Carlo simulations. We interpret the results as a manifestation of the greater stability of the spin- and valley-degenerate system against ferromagnetic instability and Wigner crystalization, which in turn suggests the existence of a new strongly correlated electron liquid at low electron densities.
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Affiliation(s)
- V. T. Renard
- Université Grenoble Alpes/CEA, INAC-SPSMS, F-38000, Grenoble, France
| | - B. A. Piot
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA-EMFL, 38042, Grenoble, France
| | - X. Waintal
- Université Grenoble Alpes/CEA, INAC-SPSMS, F-38000, Grenoble, France
| | - G. Fleury
- Service de Physique de l'État Condensé, DSM/IRAMIS/SPEC, CNRS UMR 3680 CEA Saclay, 91191 Gif sur Yvette, France
| | - D. Cooper
- Université Grenoble Alpes/CEA Leti Minatec campus, F-38054, Grenoble, France
| | - Y. Niida
- Graduate School of Science, Tohoku University, 6-3 Aramakiaza Aoba, Aobaku, Sendai, 980-8578, Japan
| | - D. Tregurtha
- Department of Physics, University of Bath, Bath, BA2 7AY, UK
| | - A. Fujiwara
- NTT Basic Research Laboratories, NTT Corporation, Atsugi-shi, Kanagawa, 243-0198, Japan
| | - Y. Hirayama
- Graduate School of Science, Tohoku University, 6-3 Aramakiaza Aoba, Aobaku, Sendai, 980-8578, Japan
| | - K. Takashina
- Department of Physics, University of Bath, Bath, BA2 7AY, UK
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5
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Islam SKF, Ghosh TK. Zero-field spin splitting in a two-dimensional electron gas with the spin-orbit interaction revisited. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:035302. [PMID: 22179301 DOI: 10.1088/0953-8984/24/3/035302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We consider a two-dimensional electron gas (2DEG) with the Rashba spin-orbit interaction (SOI) in the presence of a perpendicular magnetic field. We derive analytical expressions of the density of states (DOS) of a 2DEG with the Rashba SOI in the presence of a magnetic field by using the Green's function technique. The DOS allows us to obtain the analytical expressions of the magnetoconductivities for spin-up and spin-down electrons. The conductivities for spin-up and spin-down electrons oscillate with different frequencies and give rise to the beating patterns in the amplitude of the Shubnikov-de Haas (SdH) oscillations. We find a simple equation which determines the zero-field spin splitting energy if the magnetic field corresponding to any beat node is known from the experiment. Our analytical results reproduce well the experimentally observed non-periodic beating patterns, number of oscillations between two successive nodes and the measured zero-field spin splitting energy.
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Affiliation(s)
- S K Firoz Islam
- Department of Physics, Indian Institute of Technology-Kanpur, Kanpur, India
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6
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Zhou X, Schmidt B, Proust C, Gervais G, Pfeiffer LN, West KW, Sarma SD. Quantum-classical crossover and apparent metal-insulator transition in a weakly interacting 2D Fermi liquid. PHYSICAL REVIEW LETTERS 2011; 107:086804. [PMID: 21929191 DOI: 10.1103/physrevlett.107.086804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Indexed: 05/31/2023]
Abstract
We report the observation of an apparent parallel magnetic-field-induced metal-insulator transition in a high-mobility two-dimensional electron gas for which spin and localization physics most likely play no major role. The high-mobility metallic phase at low field is consistent with the established Fermi liquid transport theory including phonon scattering, whereas the phase at higher field shows a large insulatinglike negative temperature dependence at resistances much smaller than the quantum of resistance h/e(2). We argue that this observation is a direct manifestation of a quantum-classical crossover arising predominantly from the magneto-orbital coupling between the finite width of the two-dimensional electron gas and the in-plane magnetic field.
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Affiliation(s)
- Xiaoqing Zhou
- Department of Physics, McGill University, Montreal, H3A 2T8, Canada
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7
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Takashina K, Niida Y, Renard VT, Fujiwara A, Fujisawa T, Muraki K, Hirayama Y. Impact of valley polarization on the resistivity in two dimensions. PHYSICAL REVIEW LETTERS 2011; 106:196403. [PMID: 21668179 DOI: 10.1103/physrevlett.106.196403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Indexed: 05/30/2023]
Abstract
We examine the temperature dependence of resistivity in a two-dimensional electron system formed in a silicon-on-insulator quantum well. The device allows us to tune the valley splitting continuously in addition to the electron density. Our data provide a global picture of how the resistivity and its temperature dependence change with valley polarization. At the boundary between valley-polarized and partially polarized regions, we demonstrate that there is an insulating contribution from spin-degenerate electrons occupying the upper valley-subband edge.
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Affiliation(s)
- K Takashina
- Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
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8
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Zhou X, Piot BA, Bonin M, Engel LW, Das Sarma S, Gervais G, Pfeiffer LN, West KW. Colossal magnetoresistance in an ultraclean weakly interacting 2D Fermi liquid. PHYSICAL REVIEW LETTERS 2010; 104:216801. [PMID: 20867126 DOI: 10.1103/physrevlett.104.216801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Indexed: 05/29/2023]
Abstract
We report the observation of a new phenomenon of colossal magnetoresistance in a 40 nm wide GaAs quantum well in the presence of an external magnetic field applied parallel to the high-mobility 2D electron layer. In a strong magnetic field, the magnetoresistance is observed to increase by a factor of ∼300 from 0 to 45 T without the system undergoing any metal-insulator transition. We discuss how this colossal magnetoresistance effect cannot be attributed to the spin degree of freedom or localization physics, but most likely emanates from strong magneto-orbital coupling between the two-dimensional electron gas and the magnetic field. Our observation is consistent with a field-induced 2D-to-3D transition in the confined electronic system.
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Affiliation(s)
- Xiaoqing Zhou
- Department of Physics, McGill University, Montreal, H3A 2T8, Canada
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9
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Kawaji S. Experimental researches on quantum transport in semiconductor two-dimensional electron systems. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2008; 84:199-231. [PMID: 18941299 PMCID: PMC3666646 DOI: 10.2183/pjab.84.199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Accepted: 05/07/2008] [Indexed: 05/26/2023]
Abstract
The author reviews contribution of Gakushuin University group to the progress of the quantum transport in semiconductor two-dimensional electron systems (2DES) for forty years from the birth of the 2DES in middle of the 1960s till the finding of temperature dependent collapse of the quantized Hall resistance in the beginning of this century.
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Affiliation(s)
- Shinji Kawaji
- Department of Physics, Gakushuin University, Tokyo, Japan.
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10
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Tracy LA, Eisenstein JP, Pfeiffer LN, West KW. Spin transition in the half-filled Landau level. PHYSICAL REVIEW LETTERS 2007; 98:086801. [PMID: 17359116 DOI: 10.1103/physrevlett.98.086801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2006] [Indexed: 05/14/2023]
Abstract
The transition from partial to complete spin polarization of two-dimensional electrons at half filling of the lowest Landau level has been studied using resistively detected nuclear magnetic resonance (RDNMR). The nuclear spin-lattice relaxation time is observed to be density independent in the partially polarized phase but to increase sharply at the transition to full polarization. At low temperatures the RDNMR signal exhibits a strong maximum near the critical density.
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Affiliation(s)
- L A Tracy
- California Institute of Technology, Pasadena, CA 91125, USA
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11
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Gunawan O, Shkolnikov YP, Vakili K, Gokmen T, De Poortere EP, Shayegan M. Valley susceptibility of an interacting two-dimensional electron system. PHYSICAL REVIEW LETTERS 2006; 97:186404. [PMID: 17155564 DOI: 10.1103/physrevlett.97.186404] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2006] [Indexed: 05/12/2023]
Abstract
We report direct measurements of the valley susceptibility, the change of valley population in response to an applied symmetry-breaking strain, in an AlAs two-dimensional electron system. As the two-dimensional density is reduced, the valley susceptibility dramatically increases relative to its band value, reflecting the system's strong electron-electron interaction. The increase has a remarkable resemblance to the enhancement of the spin susceptibility and establishes the analogy between the spin and valley degrees of freedom.
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Affiliation(s)
- O Gunawan
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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12
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Pillarisetty R, Noh H, Tutuc E, Poortere EPD, Tsui DC, Shayegan M. Spin polarization dependence of the coulomb drag at large r(s). PHYSICAL REVIEW LETTERS 2005; 94:016807. [PMID: 15698117 DOI: 10.1103/physrevlett.94.016807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Indexed: 05/24/2023]
Abstract
We find that the temperature dependence of the drag resistivity between two dilute two-dimensional hole systems exhibits an unusual dependence upon spin polarization. Our main observation is that near the apparent metal-insulator transition, the temperature dependence of the drag, given by Talpha, weakens significantly with the application of a parallel magnetic field (B(||)), with alpha saturating at half its zero field value for B(||)>B(*), where B(*) is the polarization field.
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Affiliation(s)
- R Pillarisetty
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
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13
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Jaroszyński J, Popović D, Klapwijk TM. Magnetic-field dependence of the anomalous noise behavior in a two-dimensional electron system in silicon. PHYSICAL REVIEW LETTERS 2004; 92:226403. [PMID: 15245243 DOI: 10.1103/physrevlett.92.226403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2003] [Indexed: 05/24/2023]
Abstract
Studies of low-frequency resistance noise show that the dramatic change in the dynamics of the two-dimensional electron system (2DES) in Si that occurs near the metal-insulator transition (MIT) persists in high parallel magnetic fields B such that the 2DES is fully spin polarized. This strongly suggests that charge, as opposed to spin, degrees of freedom are responsible for this effect. In the metallic phase, however, noise is suppressed by a parallel B, pointing to the role of spins. At low B, the temperature dependence of conductivity in the metallic phase provides evidence for a MIT.
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Affiliation(s)
- J Jaroszyński
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA.
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Vakili K, Shkolnikov YP, Tutuc E, De Poortere EP, Shayegan M. Realization of an interacting two-valley AlAs bilayer system. PHYSICAL REVIEW LETTERS 2004; 92:186404. [PMID: 15169516 DOI: 10.1103/physrevlett.92.186404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2003] [Indexed: 05/24/2023]
Abstract
By using different widths for two AlAs quantum wells comprising a bilayer system, we force the X-point conduction-band electrons in the two layers to occupy valleys with different Fermi contours, electron effective masses, and g factors. Since the occupied valleys are at different X points of the Brillouin zone, the interlayer tunneling is negligibly small despite the close electron layer spacing. We demonstrate the realization of this system via magnetotransport measurements and the observation of a phase-coherent, bilayer nu=1 quantum Hall state flanked by a reentrant insulating phase.
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Affiliation(s)
- K Vakili
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
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15
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Pillarisetty R, Noh H, Tutuc E, De Poortere EP, Tsui DC, Shayegan M. In-plane magnetodrag between dilute two-dimensional systems. PHYSICAL REVIEW LETTERS 2003; 90:226801. [PMID: 12857330 DOI: 10.1103/physrevlett.90.226801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2003] [Indexed: 05/24/2023]
Abstract
We performed in-plane magnetodrag measurements on dilute double layer two-dimensional hole systems, at in-plane magnetic fields that suppress the apparent metallic behavior, and to fields well above those required to fully spin polarize the system. When compared to the single layer magnetoresistance, the magnetodrag exhibits exactly the same qualitative behavior. In addition, we have found that the enhancement to the drag from the in-plane field exhibits a strong maximum when both layer densities are matched.
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Affiliation(s)
- R Pillarisetty
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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16
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Zhu J, Stormer HL, Pfeiffer LN, Baldwin KW, West KW. Spin susceptibility of an ultra-low-density two-dimensional electron system. PHYSICAL REVIEW LETTERS 2003; 90:056805. [PMID: 12633387 DOI: 10.1103/physrevlett.90.056805] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2002] [Indexed: 05/24/2023]
Abstract
We determine the spin susceptibility in a two-dimensional electron system in GaAs/AlGaAs over a wide range of low densities from 2x10(9) cm(-2) to 4x10(10) cm(-2). Our data can be fitted to an equation that describes the density dependence as well as the polarization dependence of the spin susceptibility. It can account for the anomalous g factors reported recently in GaAs electron and hole systems. The paramagnetic spin susceptibility increases with decreasing density as expected from theoretical calculations.
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Affiliation(s)
- J Zhu
- Department of Physics, Columbia University, New York, New York 10027, USA
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17
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Proskuryakov YY, Savchenko AK, Safonov SS, Pepper M, Simmons MY, Ritchie DA. Hole-hole interaction effect in the conductance of the two-dimensional hole gas in the ballistic regime. PHYSICAL REVIEW LETTERS 2002; 89:076406. [PMID: 12190541 DOI: 10.1103/physrevlett.89.076406] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2001] [Indexed: 05/23/2023]
Abstract
On a high-mobility two-dimensional hole gas (2DHG) in a GaAs/GaAlAs heterostructure we study the interaction correction to the Drude conductivity in the ballistic regime, k(B)Ttau/ variant Planck's over 2pi >1. It is shown that the "metallic" behavior of the resistivity (drho/dT>0) of the low-density 2DHG is caused by the hole-hole interaction effect in this regime. We find that the temperature dependence of the conductivity and the parallel-field magnetoresistance are in agreement with this description, and determine the Fermi-liquid interaction constant Fsigma0 which controls the sign of drho/dT.
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Affiliation(s)
- Y Y Proskuryakov
- School of Physics, University of Exeter, Stocker Road, United Kingdom
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18
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Eng K, Feng XG, Popović D, Washburn S. Effects of a parallel magnetic field on the metal-insulator transition in a dilute two-dimensional electron system. PHYSICAL REVIEW LETTERS 2002; 88:136402. [PMID: 11955112 DOI: 10.1103/physrevlett.88.136402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2001] [Indexed: 05/23/2023]
Abstract
The temperature dependence of conductivity sigma(T) of a two-dimensional electron system in silicon has been studied in parallel magnetic fields B. At B = 0, the system displays a metal-insulator transition at a critical electron density n(c)(0), and dsigma/dT>0 in the metallic phase. At low fields ( B < or approximately equal to 2 T), n(c) increases as n(c)(B)-n(c)(0) proportional, variant Bbeta ( beta approximately 1), and the zero-temperature conductivity scales as sigma(n(s),B,T = 0)/sigma(n(s),0,0) = f(B(beta)/delta(n)), where delta(n) = [n(s)-n(c)(0)]/n(c)(0) and n(s) is electron density, as expected for a quantum phase transition. The metallic phase persists in fields of up to 18 T, consistent with the saturation of n(c) at high fields.
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Affiliation(s)
- Kevin Eng
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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Tutuc E, Melinte S, Shayegan M. Spin polarization and g factor of a dilute GaAs two-dimensional electron system. PHYSICAL REVIEW LETTERS 2002; 88:036805. [PMID: 11801080 DOI: 10.1103/physrevlett.88.036805] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2001] [Indexed: 05/23/2023]
Abstract
The effective g factor (g(*)) of a dilute interacting two-dimensional electron system is expected to increase with respect to its bare value as the density is lowered, and to eventually diverge as the system makes a transition to a ferromagnetic state. We report here measurements of g(*) in dilute (density 0.8 to 6.5x10(10) cm(-2)), high-mobility GaAs two-dimensional electrons from their spin polarization in a parallel magnetic field. The data reveal a surprising trend. While g(*) is indeed significantly enhanced with respect to the band g factor of GaAs, the enhancement factor decreases from about 6 to 3 as the density is reduced.
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Affiliation(s)
- E Tutuc
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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