Competing Quantum Hall Phases in the Second Landau Level in Low Density Limit

Pan, W.; Serafin, Alessandro; Xia, J. S.; Yin, Liang; Sullivan, N. S.; Baldwin, K. W.; West, K. W.; Pfeiffer, L. N.; Tsui, D. C.

doi:10.2172/1177382

Cited by 6 publications

(15 citation statements)

References 32 publications

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“…Since samples from Refs. [28,53] had a wider quantum well than our samples, the nematic in them either does not develop or it forms at a yet unknown critical κ and w/l B parameters. The other two samples, however, had quantum wells of the same width as our samples [42,52].…”

Section: Introductionmentioning

confidence: 56%

“…This was surprising, since in the second orbital Landau level at ν = 5/2 and 7/2 tilted field experiments suggested that the two ground states are close in energy [26,27]. Additionally, incipient nematicity was seen at ν = 7/2 [28]. However, a phase transition from the FQHS to the nematic in the absence of an in-plane symmetry breaking magnetic field was only recently observed [29].…”

Section: Introductionmentioning

confidence: 98%

“…[42] are disorder effects or effects due to the asymmetric shape of the wavefunction in the direction perpendicular to the plane of the electrons in gated samples. Resistance anisotropy at ν = 7/2 was, however, observed in 60 nm quantum well sample having a density of 5 × 10 10 cm −2 , providing an important clue on the influence of the width of the quantum well [28]. No data is available at ν = 7/2 in Refs.…”

Section: Introductionmentioning

confidence: 99%

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Electron–electron interactions and the paired-to-nematic quantum phase transition in the second Landau level

et al. 2018

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In spite of its ubiquity in strongly correlated systems, the competition of paired and nematic ground states remains poorly understood. Recently such a competition was reported in the two-dimensional electron gas at filling factor ν = 5/2. At this filling factor a pressure-induced quantum phase transition was observed from the paired fractional quantum Hall state to the quantum Hall nematic. Here we show that the pressure-induced paired-to-nematic transition also develops at ν = 7/2, demonstrating therefore this transition in both spin branches of the second orbital Landau level. However, we find that pressure is not the only parameter controlling this transition. Indeed, ground states consistent with those observed under pressure also develop in a sample measured at ambient pressure, but in which the electron–electron interaction was tuned close to its value at the quantum critical point. Our experiments suggest that electron–electron interactions play a critical role in driving the paired-to-nematic transition.

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Section: Introductionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Electron–electron interactions and the paired-to-nematic quantum phase transition in the second Landau level

et al. 2018

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“…In contrast, the development of the ordered phase with the application of an external magnetic field is not associated with a thermodynamic singularity. In the 2DEG spontaneous anisotropy develops in the absence of any externally applied symmetry breaking fields at ν = 9/2, 11/2, 13/2, 15/2, ... [5][6][7] and also at ν = 7/2 [30] at low enough temperatures. The ground state at these filling factors is the well-known quantum Hall nematic phase, also referred to in the literature as the stripe phase [1,2].…”

mentioning

confidence: 99%

Observation of a transition from a topologically ordered to a spontaneously broken symmetry phase

Samkharadze¹,

Schreiber²,

Gardner³

et al. 2015

Nature Phys

112

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Until the late 1980s, phases of matter were understood in terms of Landau's symmetry breaking theory. Following the discovery of the quantum Hall effect the introduction of a second class of phases, those with topological order, was necessary. Phase transitions within the first class of phases involve a change in symmetry, whereas those between topological phases require a change in topological order. However, in rare cases transitions may occur between the two classes in which the vanishing of the topological order is accompanied by the emergence of a broken symmetry. Here, we report the existence of such a transition in the two-dimensional electron gas. When tuned by hydrostatic pressure, the ν = 5/2 fractional quantum Hall state, believed to be a prototype non-Abelian topological phase, gives way to a quantum Hall nematic phase. Remarkably, this nematic phase develops spontaneously, i.e. in the absence of any externally applied symmetry breaking fields.

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“…The related studies at the 5/2 state have found much stronger evidence for spin-polarization than spin-unpolarization in open geometry samples (29)(30)(31)(32)(33)(34)(35)(36)(37). It should be noted that such an energy gap measurement (28) was studied at magnetic field lower than 1 T, and another measurement at magnetic field similar to this work only showed monotonic behavior between the energy gap and the density (38). Lastly, the electrostatic potential caused by the gates will certainly not be constant over the width of the confined region, and its shape may influence the relative stability of the two states.…”

Section: Discussionmentioning

confidence: 91%

Competing ν = 5/2 fractional quantum Hall states in confined geometry

Wang

Shan

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Some theories predict that the filling factor 5/2 fractional quantum Hall state can exhibit non-Abelian statistics, which makes it a candidate for fault-tolerant topological quantum computation. Although the non-Abelian Pfaffian state and its particle-hole conjugate, the anti-Pfaffian state, are the most plausible wave functions for the 5/2 state, there are a number of alternatives with either Abelian or non-Abelian statistics. Recent experiments suggest that the tunneling exponents are more consistent with an Abelian state rather than a non-Abelian state. Here, we present edge-current-tunneling experiments in geometrically confined quantum point contacts, which indicate that Abelian and non-Abelian states compete at filling factor 5/2. Our results are consistent with a transition from an Abelian state to a non-Abelian state in a single quantum point contact when the confinement is tuned. Our observation suggests that there is an intrinsic non-Abelian 5/2 ground state but that the appropriate confinement is necessary to maintain it. This observation is important not only for understanding the physics of the 5/2 state but also for the design of future topological quantum computation devices.fractional quantum Hall effect | 5/2 fractional quantum Hall state | edge-current tunneling | quantum point contact | non-Abelian statistics A mong the roughly 100 known fractional quantum Hall (FQH) states, the filling factor ν = 5/2 state is special. It is an evendenominator state with elementary excitations that may have nonAbelian statistics (1-10). If the ground state is non-Abelian, it would be insensitive to environmental decoherence (11) and would therefore be useful for fault-tolerant topological quantum computation. Because of this potential application, much theoretical effort has focused on the 5/2 state, and a variety of wave functions have been proposed (1-3, 5-7, 12-15). There have also been several experiments on the 5/2 state, with more of them supporting non-Abelian than Abelian statistics (16,17). All of the proposed wave functions for the 5/2 state have an effective charge e* of the quasiparticles that is a quarter of the elementary charge e, and this effective charge has been confirmed experimentally (18-21). However, the wave function of the 5/2 state is still under discussion.The proposed wave functions of the 5/2 state can be distinguished by the strength of the interaction between quasiparticles, described by a coupling constant g. This coupling constant can be obtained from experiments using weak-tunneling theory (22). The FQH effect emerges in a highly interacting 2D electron gas (2DEG) at high magnetic field and ultralow temperature. The FQH states have gapless conducting edge currents at the boundaries of the 2DEG, in which fractionally charged quasiparticles carry the current. If the counter-propagating edge currents of a FQH state are brought close enough together in a quantum point contact (QPC), back-scattering is induced. In the weak-tunneling regime, the rate of quasiparticle tunneling depend...

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Competing Quantum Hall Phases in the Second Landau Level in Low Density Limit

Cited by 6 publications

References 32 publications

Electron–electron interactions and the paired-to-nematic quantum phase transition in the second Landau level

Electron–electron interactions and the paired-to-nematic quantum phase transition in the second Landau level

Observation of a transition from a topologically ordered to a spontaneously broken symmetry phase

Competing ν = 5/2 fractional quantum Hall states in confined geometry

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