Anomalous temperature dependence of the correlated ν=1 quantum Hall effect in bilayer electron systems

Lay, T. S.; Suen, Y. W.; Manoharan, Hari C.; Ying, Xiao; Santos, M. B.; Shayegan, M.

doi:10.1103/physrevb.50.17725

Cited by 61 publications

(67 citation statements)

References 17 publications

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“…Explicit interlayer correlations are present in the fractional quantum Hall state at total Landau level filling ν = 1/2 1-5 as well as the celebrated bilayer excitonic condensate state at ν = 1 [4][5][6][7][8][9][10][11][12][13][14] . The ν = 1 excitonic condensate state is seen for small layer separation and an interlayer sufficiently large that interlayer tunneling is negligible.…”

Section: Introductionmentioning

confidence: 99%

Unequal layer densities in bilayer Wigner crystal at high magnetic fields

et al. 2012

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We report studies of pinning mode resonances of magnetic field induced bilayer Wigner crystals of bilayer hole samples with negligible interlayer tunneling and different interlayer separations d, in states with varying layer densities, including unequal layer densities. With unequal layer densities, samples with large d relative to the in-plane carrier-carrier spacing a, two pinning resonances are present, one for each layer. For small d/a samples, a single resonance is observed even with significant density imbalance. These samples, at balance, were shown to exhibit an enhanced pinning mode frequency [Zhihai Wang et al., Phys. Rev. Lett. 136804 (2007)], which was ascribed to a onecomponent, pseudospin ferromagnetic Wigner solid. The evolution of the resonance frequency and line width indicates the quantum interlayer coherence survives at moderate density imbalance, but disappears when imbalance is sufficiently large.

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Section: Introductionmentioning

confidence: 99%

Unequal layer densities in bilayer Wigner crystal at high magnetic fields

et al. 2012

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“…A very interesting example [1][2][3] occurs for electron bilayers in the quantum Hall regime. When the two layers are close and have individual filling factors =1/ 2, the Coulomb interactions produce a ground state in which electrons in one layer are correlated with holes in the other.…”

Section: Introductionmentioning

confidence: 99%

Vortex states of a disordered quantum Hall bilayer

2009

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We present and solve a model for the vortex configuration of a disordered quantum Hall bilayer in the limit of strong and smooth disorder. We argue that there is a characteristic disorder strength below which vortices will be rare and above which they proliferate. We predict that this can be observed tuning the electron density in a given sample. The ground state in the strong-disorder regime can be understood as an emulsion of vortex-antivortex crystals. Its signatures include a suppression of the spatial decay of counterflow currents. We find an increase of at least an order of magnitude in the length scale for this decay compared to a clean system. This provides a possible explanation of the apparent absence of leakage of counterflow currents through interlayer tunneling, even in experiments performed deep in the coherent phase where enhanced interlayer tunneling is observed.

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“…Numerous interesting properties are anticipated, including linearly dispersing Goldstone collective modes (i.e., pseudospin waves), a finite temperature Kosterlitz-Thouless transition, dissipationless transport for currents directed oppositely in the two layers, and bizarre topological defects in the pseudospin field [9][10][11][12][13]. To date, most experimental results on this system have derived from electrical transport measurements [3,4,7,14,15] although recently an optical study has been reported [16].…”

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Resonantly Enhanced Tunneling in a Double Layer Quantum Hall Ferromagnet

Spielman

Eisenstein

Pfeiffer³

et al. 2000

Phys. Rev. Lett.

469

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The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations. At total Landau level filling n T 1 the tunnel spectrum changes qualitatively when the boundary separating the compressible phase from the ferromagnetic quantized Hall state is crossed. A huge resonant enhancement replaces the strongly suppressed equilibrium tunneling characteristic of weakly coupled layers. The possible relationship of this enhancement to the Goldstone mode of the broken symmetry ground state is discussed. PACS numbers: 71.10.Pm, 73.40.Hm, 73.40.Gk When two parallel two-dimensional electron systems (2DES) are sufficiently close together, interlayer Coulomb interactions can produce collective states which have no counterpart in the individual 2D systems [1][2][3]. One of the simplest, yet most interesting, examples occurs when the total electron density, N T , equals the degeneracy, eB͞h, of a single spin-resolved Landau level produced by a magnetic field B. In the balanced case (i.e., with layer densities N 1 N 2 N T ͞2), the Landau level filling factor of each layer viewed separately is n hN T ͞2eB 1͞2. If the separation d between the layers is large, they behave independently and are well described as gapless composite fermion liquids. No quantized Hall effect (QHE) is seen. On the other hand, as d is reduced, the system undergoes a quantum phase transition [4-6] to an incompressible state best described by the total filling factor n T 1͞2 1 1͞2 1. A quantized Hall plateau now appears at r xy h͞e 2 . Both Coulomb interactions and interlayer tunneling contribute to the strength of this QHE but there is strong evidence from experiment [3,7] and theory [1,8] that the incompressibility survives in the limit of zero tunneling. This remarkable collective state exhibits a broken symmetry [9][10][11][12], spontaneous interlayer phase coherence, and may be viewed as a kind of easy-plane ferromagnet. The magnetization of this ferromagnet exists in a pseudospin space; electrons in one layer are pseudospin up, while those in the other layer are pseudospin down. Numerous interesting properties are anticipated, including linearly dispersing Goldstone collective modes (i.e., pseudospin waves), a finite temperature Kosterlitz-Thouless transition, dissipationless transport for currents directed oppositely in the two layers, and bizarre topological defects in the pseudospin field [9][10][11][12][13]. To date, most experimental results on this system have derived from electrical transport measurements [3,4,7,14,15] although recently an optical study has been reported [16].In this paper we report on a new study of the double layer n T 1 ferromagnetic quantum Hall state, and its transition at large layer separation to a compressible phase, using the method of tunneling spectroscopy. Earlier experiments have shown that there is a strong suppression of the equilibrium tunneling between two widely separated parallel 2DESs at high magnetic field [17,18]. This suppression is a ...

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Anomalous temperature dependence of the correlated ν=1 quantum Hall effect in bilayer electron systems

Cited by 61 publications

References 17 publications

Unequal layer densities in bilayer Wigner crystal at high magnetic fields

Unequal layer densities in bilayer Wigner crystal at high magnetic fields

Vortex states of a disordered quantum Hall bilayer

Resonantly Enhanced Tunneling in a Double Layer Quantum Hall Ferromagnet

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