Nonconventional Odd-Denominator Fractional Quantum Hall States in the Second Landau Level

Kumar, Ashwani; Csáthy, Gábor; Manfra, Michael J.; Pfeiffer, L. N.; West, K. W.

doi:10.1103/physrevlett.105.246808

Cited by 142 publications

(194 citation statements)

References 48 publications

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“…The fits suggest a competition between L 2 and L 3 , with the L 3 gaining intensity and L 2 shrinking with increasing temperature. This temperature dependence is significantly weaker than that of FQHE and RIQHE [44] and is more similar to the temperature dependence of anisotropic transport at ν = 7/3 [23].…”

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confidence: 80%

Optical Emission Spectroscopy Study of Competing Phases of Electrons in the Second Landau Level

et al. 2016

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Quantum phases of electrons in the filling factor range 2 ≤ ν ≤ 3 are probed by the weak optical emission from the partially populated second Landau level and spin wave measurements. Observations of optical emission include a multiplet of sharp peaks that exhibit a strong filling factor dependence. Spin wave measurements by resonant inelastic light scattering probe breaking of spin rotational invariance and are used to link this optical emission with collective phases of electrons. A remarkably rapid interplay between emission peak intensities manifests phase competition in the second Landau level.Ultra-clean two dimensional electron systems in the presence of high perpendicular magnetic fields B are a source of unexpected and fascinating quantum many-body physics that arises from the strong electron interactions combined with a reduction in dimensionality. When B is high enough for all electrons to occupy the lowest (N=0) Landau level (LL), the many-electron system forms liquids of the fractional quantum Hall effect (FQHE). When B is such that electrons fill states in higher (N ≥ 2) LL's, electrons form quantum phases referred to as stripe and bubble phases, which lead to transport anisotropy and reentrant integer quantum Hall effect (RIQHE) states [1][2][3]. The unique electron-electron interactions in the N=1 LL result in the presence of RIQHE states and stripe phases in addition to even-and odd-denominator FQHE states [3,4]. FQHE states in the second (N=1) LL exhibit evendenominator states such as the one at ν = 5/2 [5, 6], which is predicted to have non-Abelian excitations [7][8][9][10][11][12][13][14], has recently been studied by NMR [15,16], by light scattering methods [17,18], and in two-subband systems [19]. It has been predicted that the less studied FQHE state at ν = 2 + 1/3 = 7/3 could possess exotic quasiparticles in which composite fermions are dressed by a cloud of neutral excitations [20]. Since FQHE liquids as well as bubble and stripe phases can serve as ground states, the N=1 LL is home to a striking competition between quantum phases [21].The interplay of anisotropic phases with FQHE liquids in the second LL has been studied by introduction of in-plane magnetic fields [3,[22][23][24][25]. These experiments provide evidence that anisotropic smectic-or nematic-like phases with broken full rotational invariance coexist with quantum Hall liquids [26][27][28][29][30]. The large anisotropy induced in the system at the FQHE states at ν = 5/2 and ν = 7/3 by relatively small in-plane magnetic fields [22][23][24] supports interpretations in terms of a new state of electron matter with FQHE states that occur in the environment of a nematic stripe phase [30][31][32].We report optical emission experiments that probe quantum phases that emerge in the second LL of an ultra-clean 2D electron system. The optical recombination is from transitions across conduction to valence band states from electrons that partially populate the N=1 LL. This emission, while much weaker than the one originating in the N=0 LL (...

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Optical Emission Spectroscopy Study of Competing Phases of Electrons in the Second Landau Level

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“…This FQHS was discovered 1 and studied in depth in high quality two-dimensional electron gases (2DEGs) confined to GaAs/AlGaAs heterostructures . Other even denominator FQHSs in the GaAs/AlGaAs system develop at ν = 7/2 6,16,40,41 and ν = 2 + 3/8 [42][43][44] and possibly related FQHSs have been observed at even denominators in ZnO/MgZnO 45 and in bilayer graphene [46][47][48][49] . Since its discovery it was clear that, owing to the even denominator of the filling factor, the ν = 5/2 FQHS is not part of the sequence prescribed by the free composite fermion theory 50,51 .…”

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Observation of an anomalous density-dependent energy gap of the ν=5/2 fractional quantum Hall state in the low-density regime

Samkharadze¹,

Ro²,

Pfeiffer³

et al. 2017

Phys. Rev. B

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We have studied the ν = 5/2 fractional quantum Hall state in a density-tunable sample at extremely low electron densities. For the densities accessed in our experiment, the Landau level mixing parameter κ spans the 2.52 < κ < 2.82 range. In the vicinity of 5.8 × 10 10 cm −2 or κ = 2.6 an anomalously large change in the density dependence of the energy gap is observed. Possible origins of such an anomaly are discussed, including a topological phase transition in the ν = 5/2 fractional quantum Hall state.

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“…Indeed, Willett and collaborators [8] demonstrated the existence of a Fermi surface at ν = 5/2 at T=0.3K using surface acoustic wave techniques. The CF model has also been successfully used to analyze energy gaps of odd denominator FQHSs around ν = 5/2 by using the CF cyclotron energy [20,21]. In the CF picture, the fractional quantum Hall state that emerges at T≤100mK is viewed as a condensation of CFs driven by a BCS-like p-wave pairing instability [31,32].…”

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High-temperature resistivity measured at ν=52 as a predictor of the two-dimensional electron gas quality in the N=1 Landau level

et al. 2017

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We report a high temperature (T = 0.3K) indicator of the excitation gap ∆ 5/2 at the filling factor ν = 5/2 fractional quantum Hall state in ultra-high quality AlGaAs/GaAs two-dimensional electron gases. As the lack of correlation between mobility µ and ∆ 5/2 has been well established in previous experiments, we define, analyze and discuss the utility of a different metric ρ 5/2 , the resistivity at ν = 5/2, as a high temperature predictor of ∆ 5/2 . This high-field resistivity reflects the scattering rate of composite fermions. Good correlation between ρ 5/2 and ∆ 5/2 is observed in both a density tunable device and in a series of identically structured wafers with similar density but vastly different mobility. This correlation can be explained by the fact that both ρ 5/2 and ∆ 5/2 are sensitive to long-range disorder from remote impurities, while µ is sensitive primarily to disorder localized near the quantum well.

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Nonconventional Odd-Denominator Fractional Quantum Hall States in the Second Landau Level

Cited by 142 publications

References 48 publications

Optical Emission Spectroscopy Study of Competing Phases of Electrons in the Second Landau Level

Optical Emission Spectroscopy Study of Competing Phases of Electrons in the Second Landau Level

Observation of an anomalous density-dependent energy gap of the ν=5/2 fractional quantum Hall state in the low-density regime

High-temperature resistivity measured at ν=52 as a predictor of the two-dimensional electron gas quality in the N=1 Landau level

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