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Eisenstein JP, Pfeiffer LN, West KW. Precursors to Exciton Condensation in Quantum Hall Bilayers. PHYSICAL REVIEW LETTERS 2019; 123:066802. [PMID: 31491172 DOI: 10.1103/physrevlett.123.066802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Indexed: 06/10/2023]
Abstract
Tunneling spectroscopy reveals evidence for interlayer electron-hole correlations in quantum Hall bilayer two-dimensional electron systems at layer separations near, but above, the transition to the incompressible exciton condensate at total Landau level filling ν_{T}=1. These correlations are manifested by a nonlinear suppression of the Coulomb pseudogap which inhibits low energy interlayer tunneling in weakly coupled bilayers. The pseudogap suppression is strongest at ν_{T}=1 and grows rapidly as the critical layer separation for exciton condensation is approached from above.
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Affiliation(s)
- J P Eisenstein
- Institute for Quantum Information and Matter, Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - L N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - K W West
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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2
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Chowdhury D, Skinner B, Lee PA. Effect of Magnetization on the Tunneling Anomaly in Compressible Quantum Hall States. PHYSICAL REVIEW LETTERS 2018; 120:266601. [PMID: 30004777 DOI: 10.1103/physrevlett.120.266601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Indexed: 06/08/2023]
Abstract
Tunneling of electrons into a two-dimensional electron system is known to exhibit an anomaly at low bias, in which the tunneling conductance vanishes due to a many-body interaction effect. Recent experiments have measured this anomaly between two copies of the half-filled Landau level as a function of in-plane magnetic field, and they suggest that increasing spin polarization drives a deeper suppression of tunneling. Here, we present a theory of the tunneling anomaly between two copies of the partially spin-polarized Halperin-Lee-Read state, and we show that the conventional description of the tunneling anomaly, based on the Coulomb self-energy of the injected charge packet, is inconsistent with the experimental observation. We propose that the experiment is operating in a different regime, not previously considered, in which the charge-spreading action is determined by the compressibility of the composite fermions.
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Affiliation(s)
- Debanjan Chowdhury
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Patrick A Lee
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Tiemann L, Wegscheider W, Hauser M. Electron spin polarization by isospin ordering in correlated two-layer quantum Hall systems. PHYSICAL REVIEW LETTERS 2015; 114:176804. [PMID: 25978250 DOI: 10.1103/physrevlett.114.176804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Indexed: 06/04/2023]
Abstract
Enhancement of the electron spin polarization in a correlated two-layer, two-dimensional electron system at a total Landau level filling factor of 1 is reported. Using resistively detected nuclear magnetic resonance, we demonstrate that the electron spin polarization of two closely spaced two-dimensional electron systems becomes maximized when interlayer Coulomb correlations establish spontaneous isospin ferromagnetic order. This correlation-driven polarization dominates over the spin polarizations of competing single-layer fractional quantum Hall states under electron density imbalances.
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Affiliation(s)
- L Tiemann
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - M Hauser
- Max-Planck-Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
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Hayward ALC, Martin AM, Greentree AD. Fractional quantum Hall physics in Jaynes-Cummings-Hubbard lattices. PHYSICAL REVIEW LETTERS 2012; 108:223602. [PMID: 23003593 DOI: 10.1103/physrevlett.108.223602] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Indexed: 06/01/2023]
Abstract
Jaynes-Cummings-Hubbard arrays provide unique opportunities for quantum emulation as they exhibit convenient state preparation and measurement, as well as in situ tuning of parameters. We show how to realize strongly correlated states of light in Jaynes-Cummings-Hubbard arrays under the introduction of an effective magnetic field. The effective field is realized by dynamic tuning of the cavity resonances. We demonstrate the existence of Laughlin-like fractional quantum Hall states by computing topological invariants, phase transitions between topologically distinct states, and Laughlin wave function overlap.
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Giudici P, Muraki K, Kumada N, Fujisawa T. Intrinsic gap and exciton condensation in the nu{T}=1 bilayer system. PHYSICAL REVIEW LETTERS 2010; 104:056802. [PMID: 20366783 DOI: 10.1103/physrevlett.104.056802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 12/16/2009] [Indexed: 05/29/2023]
Abstract
We investigate the quasiparticle excitation of the bilayer quantum Hall (QH) system at a total filling factor nu{T}=1 in the limit of negligible interlayer tunneling under a tilted magnetic field. We show that the intrinsic quasiparticle excitation is of purely pseudospin origin and solely governed by the inter- and intralayer electron interactions. A model based on exciton formation successfully explains the quantitative behavior of the quasiparticle excitation gap, demonstrating the existence of a link between the excitonic QH state and the composite fermion liquid. Our results provide a new insight into the nature of the phase transition between the two states.
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Affiliation(s)
- P Giudici
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi 243-0198, Japan
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Finck ADK, Eisenstein JP, Pfeiffer LN, West KW. Quantum Hall exciton condensation at full spin polarization. PHYSICAL REVIEW LETTERS 2010; 104:016801. [PMID: 20366378 DOI: 10.1103/physrevlett.104.016801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Indexed: 05/29/2023]
Abstract
Using Coulomb drag as a probe, we explore the excitonic phase transition in quantum Hall bilayers at nu(T) = 1 as a function of Zeeman energy E(Z). The critical layer separation (d/l)(c) for exciton condensation initially increases rapidly with E(Z), but then reaches a maximum and begins a gentle decline. At high E(Z), where both the excitonic phase at small d/l and the compressible phase at large d/l are fully spin polarized, we find that the width of the transition, as a function of d/l, is much larger than at small E(Z) and persists in the limit of zero temperature. We discuss these results in the context of two models in which the system contains a mixture of the two fluids.
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Affiliation(s)
- A D K Finck
- Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125, USA
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Alicea J, Motrunich OI, Refael G, Fisher MPA. Interlayer coherent composite Fermi liquid phase in quantum Hall bilayers. PHYSICAL REVIEW LETTERS 2009; 103:256403. [PMID: 20366269 DOI: 10.1103/physrevlett.103.256403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Indexed: 05/29/2023]
Abstract
We introduce an interlayer coherent composite Fermi liquid for nu = 1/2 + 1/2 bilayers, in which interlayer Coulomb repulsion drives exciton condensation of composite fermions. As a result, composite fermions propagate coherently between layers--even though electrons do not--and form bonding and antibonding Fermi seas. This phase is compressible with respect to symmetric currents but quantum Hall-like in the counterflow channel. Quantum oscillations of the composite Fermi seas generate a new series of incompressible states at nu = p/[2(p +/- 1)] per layer (p an integer), which is a bilayer analogue of Jain's sequence.
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Affiliation(s)
- Jason Alicea
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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Li YQ, Umansky V, von Klitzing K, Smet JH. Nature of the spin transition in the half-filled Landau level. PHYSICAL REVIEW LETTERS 2009; 102:046803. [PMID: 19257456 DOI: 10.1103/physrevlett.102.046803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Indexed: 05/27/2023]
Abstract
We report transport and nuclear spin relaxation studies of a density tunable two-dimensional electron system at filling nu=1/2 in tilted magnetic fields. The transition from partial to full spin polarization with an in-plane field leaves a clear signature in the resistance. Nuclear spin relaxation studies suggest that puddles of minority spins are responsible for an observed non-Korringa temperature dependence. This inhomogeneous spin polarization, similarly encountered in manganites where it strongly affects resistance, may help with understanding the spin dependent transport at nu=1/2.
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Affiliation(s)
- Y Q Li
- Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
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Karmakar B, Pellegrini V, Pinczuk A, Pfeiffer LN, West KW. First-order quantum phase transition of excitons in quantum Hall bilayers. PHYSICAL REVIEW LETTERS 2009; 102:036802. [PMID: 19257378 DOI: 10.1103/physrevlett.102.036802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Indexed: 05/27/2023]
Abstract
We show that the quantum phase transformation between compressible metallic and incompressible excitonic states in the coupled bilayers at total Landau level filling factor nuT=1 becomes discontinuous (first order) by impacts of different terms of the electron-electron interactions that prevail on weak residual disorder. The evidence is based on precise determinations of the excitonic order parameter by inelastic light scattering measurements close to the phase boundary. While there is marked softening of low-lying excitations, our experiments underpin the roles of competing order parameters linked to quasiparticle correlations in removing the divergence of quantum fluctuations.
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Murthy G, Sachdev S. Quantum Hall to insulator transition in the bilayer quantum Hall ferromagnet. PHYSICAL REVIEW LETTERS 2008; 101:226801. [PMID: 19113502 DOI: 10.1103/physrevlett.101.226801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Indexed: 05/27/2023]
Abstract
We describe a phase transition of the bilayer quantum Hall ferromagnet at nu=1. In the presence of static disorder (modeled by a periodic potential), bosonic S=1/2 spinons undergo a superfluid-insulator transition while preserving ferromagnetism. The Mott insulating phase has an emergent U(1) photon, and the transition is between Higgs and Coulomb phases of this photon. Consequences for charge and counterflow conductivity and for interlayer tunneling conductance are discussed.
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Affiliation(s)
- Ganpathy Murthy
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055, USA
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Giudici P, Muraki K, Kumada N, Hirayama Y, Fujisawa T. Spin-dependent phase diagram of the nuT=1 bilayer electron system. PHYSICAL REVIEW LETTERS 2008; 100:106803. [PMID: 18352219 DOI: 10.1103/physrevlett.100.106803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Indexed: 05/26/2023]
Abstract
We show that the spin degree of freedom plays a decisive role in the phase diagram of the nu(T)=1 bilayer electron system using an in-plane field B( parallel) in the regime of negligible tunneling. We observe that the phase boundary separating the quantum Hall and compressible states at d/l(B) = 1.90 for B(parallel) = 0 (d: interlayer distance, l(B): magnetic length) steadily shifts with B(parallel) before saturating at d/l(B) = 2.33 when the compressible state becomes fully polarized. Using a simple model for the energies of the competing phases, we can quantitatively describe our results. A new phase diagram as a function of d/l(B) and the Zeeman energy is established and its implications as to the nature of the phase transition are discussed.
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Affiliation(s)
- P Giudici
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi 243-0198, Japan
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Champagne AR, Eisenstein JP, Pfeiffer LN, West KW. Evidence for a finite-temperature phase transition in a bilayer quantum Hall system. PHYSICAL REVIEW LETTERS 2008; 100:096801. [PMID: 18352740 DOI: 10.1103/physrevlett.100.096801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Indexed: 05/26/2023]
Abstract
We study the Josephson-like interlayer tunneling signature of the strongly correlated nuT=1 quantum Hall phase in bilayer two-dimensional electron systems as a function of the layer separation, temperature, and interlayer charge imbalance. Our results offer strong evidence that a finite temperature phase transition separates the interlayer coherent phase from incoherent phases which lack strong interlayer correlations. The transition temperature is dependent on both the layer spacing and charge imbalance between the layers.
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Affiliation(s)
- A R Champagne
- Condensed Matter Physics, California Institute of Technology, Pasadena CA 91125, USA
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Zhang XC, Scott GD, Jiang HW. NMR probing of spin excitations in the ring structure of a two-subband system. PHYSICAL REVIEW LETTERS 2007; 98:246802. [PMID: 17677981 DOI: 10.1103/physrevlett.98.246802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Indexed: 05/16/2023]
Abstract
Resistively detected nuclear magnetic resonance (NMR) is observed inside the ringlike structure, with a quantized Hall conductance of 6e(2)/h, in the phase diagram of a two-subband electron system. The NMR signal persists up to 470 mK and is absent in other states with the same quantized Hall conductance. The nuclear spin-lattice relaxation time T1, is found to decrease rapidly towards the ring center. A strong dynamic nuclear polarization by the biasing current has also been observed only inside the ring. These observations are consistent with the assertion of the ringlike region being a ferromagnetic state that is accompanied by collective spin excitations.
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Affiliation(s)
- X C Zhang
- Department of Physics and Astronomy, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA
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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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Vakili K, Gokmen T, Gunawan O, Shkolnikov YP, De Poortere EP, Shayegan M. Dependence of persistent gaps at landau level crossings on relative spin. PHYSICAL REVIEW LETTERS 2006; 97:116803. [PMID: 17025916 DOI: 10.1103/physrevlett.97.116803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Indexed: 05/12/2023]
Abstract
We report measurements of the quantum Hall state energy gap at avoided crossings between Landau levels originating from different conduction band valleys in AlAs quantum wells. These gaps exhibit an approximately linear dependence on the magnetic field over a wide range of fields and filling factors. More remarkably, we observe an unexpected dependence of the gap size on the relative spin orientation of the crossing levels, with parallel-spin crossings exhibiting larger gaps than antiparallel-spin crossings.
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Affiliation(s)
- K Vakili
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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