<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">SU</mml:mi><mml:mo>(</mml:mo><mml:mn>4</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:math>skyrmions and activation energy anomaly in bilayer quantum Hall systems

Ezawa, Zyun F.; Tsitsishvili, G.

doi:10.1103/physrevb.70.125304

Cited by 23 publications

(16 citation statements)

References 36 publications

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“…Since the spin degree of freedom is not frozen in CF liquids, these theories may provide an important clue. Another possibility may be an excitation including both spin and pseudospin [23]. Further discussion on this issue, however, is beyond the scope of this Letter.…”

mentioning

confidence: 99%

Spin Degree of Freedom in theν=1Bilayer Electron System Investigated by Nuclear Spin Relaxation

Kumada

Muraki

Hashimoto³

et al. 2005

Phys. Rev. Lett.

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The nuclear-spin-relaxation rate 1/T1 has been measured in a bilayer electron system at and around total Landau level filling factor ν = 1. The measured 1/T1, which probes electron spin fluctuations, is found to increase gradually from the quantum Hall (QH) state at low fields through a phase transition to the compressible state at high fields. Furthermore, 1/T1 in the QH state shows a small but noticeable increase away from ν = 1. These results demonstrate that, as opposed to common assumption, the electron spin degree of freedom is completely frozen neither in the QH nor compressible states.The bilayer electron system at total Landau level filling factor ν = 1 (1/2 in each layer) have been continuously drawing intensive research interest because of its unique phase diagram [1,2]. Two parameters play crucial role: the ratio of the intralayer to interlayer Coulomb interactions, given by the ratio between the interlayer distance d and the magnetic length l B = /eB (and hence controlled by the magnetic field B), and the tunneling gap ∆ SAS . For d/l B below a certain critical value, strong interlayer interactions lead to a many-body quantum Hall (QH) state even in the limit of zero tunneling gap, supported by spontaneous interlayer coherence [3]. When intralayer interactions dominate at larger d/l B , in contrast, the QH state collapses into a compressible state having lower intralayer correlation energy even for finite ∆ SAS [4]. Recent interests have focused on the nature of the phase transition between these limits. Interlayer tunneling [3] and Coulomb drag [5] experiments carried out on samples with vanishingly small ∆ SAS have revealed that below a critical d/l B the interlayer coherence develops somewhat continuously, in contrast to the result of a numerical study [6] that the transition is likely to be first order at any value of ∆ SAS . In spite of various theoretical models [7,8,9, 10] motivated by these findings, a comprehensive understanding is not yet achieved.In all these theories, it is routinely assumed that the spin degree of freedom is frozen by the Zeeman coupling to the magnetic field, and physics is governed solely by the pseudospin representing the layer degree of freedom. This assumption seems reasonable for the QH state, and is indeed verified by numerical calculation [6]. We note, however, that because of the small g-factor in GaAs, a monolayer two-dimensional electron system (2DES) at ν = 1/2 is not fully spin polarized in the relevant magnetic field region, B 10 T [11,12,13]. Hence, if the bilayer ν = 1 compressible state consists of two indepen- * Present address: Institute of Applied Physics, Hamburg University, Jungiusstrasse 11, D-20355 Hamburg, Germany. dent monolayers of 1/2 fillings, the phase transition must be accompanied by changes not only in the pseudospin but also in the spin configurations. While spin states in monolayer systems have been studied by various optical means [11], little is known about the spin states in bilayer systems, presumably because of the difficulty in i...

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confidence: 99%

Spin Degree of Freedom in theν=1Bilayer Electron System Investigated by Nuclear Spin Relaxation

Kumada

Muraki

Hashimoto³

et al. 2005

Phys. Rev. Lett.

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“…The SU(N ) extension of the magnetic translation group, T M × SU(N ), with N ≥ 4, was indeed the starting point of several other theoretical works on bilayer quantum Hall systems. 22,23,28,29 We have thus shown that a SU(4) description of the texture states is necessary even if the ground state has the reduced internal symmetry SU(2)×SU(2).…”

Section: Discussionmentioning

confidence: 98%

“…The energetics of the resulting topological excitations has been an active field of study in recent years. 25,26,27,28,29,30,31 In this paper, we consider the properties of SU(2)×SU(2) Skyrmions in the presence of realistic anisotropy terms. We do this from a perspective of entanglement between the spin and pseudospin degrees of freedom.…”

Section: Introductionmentioning

confidence: 99%

Entanglement skyrmions in multicomponent quantum Hall systems

et al. 2008

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We discuss charged topological spin textures in quantum Hall ferromagnets in which the electrons carry an pseudospin as well as the usual spin degree of freedom, as is the case in bilayer GaAs or monolayer graphene samples. We develop a theory which treats spin and pseudospin on a manifestly equal footing, which may also be of help in visualizing the relevant spin textures. We in particular consider the entanglement of spin and pseudospin in the presence of realistic anisotropies. An entanglement operator is introduced which generates families of degenerate Skyrmions with differing entanglement properties. We propose a local characterization of the latter, and touch on the role entangled Skyrmions play in the nuclear relaxation time of quantum Hall ferromagnets.

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“…What are observed experimentally are the classical densities, which are expectation values such as ρ cl (p) = ⟨S|ρ(p)|S⟩, where |S⟩ represents a generic state in the LLL. The SU(4) effective Hamiltonian density are given by [3] …”

Section: The Su(4) Effective Hamiltonian and The Ground State Structurementioning

confidence: 99%

“…The ground state structure of the ν = 2 bilayer QH system has been investigated based on the SU(4) formalism [3,4]. However, the effective Hamiltonian for the Goldstone modes has not been derived, especially in the CAF phase.…”

Section: Introductionmentioning

confidence: 99%

Goldstone Modes in Bilayer Quantum Hall Systems at ν = 2

Hama

Hidaka

Tsitsishvili

et al. 2013

J. Phys.: Conf. Ser.

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Abstract. At the filling factor ν=2, the bilayer quantum Hall system has three phases, the spin-ferromagnet phase, the spin singlet phase and the canted antiferromagnet (CAF) phase, depending on the relative strength between the Zeeman energy and interlayer tunneling energy. We present a systematic method to derive the effective Hamiltonian for the Goldstone modes in these three phases. We then investigate the dispersion relations and the coherence lengths of the Goldstone modes. To explore a possible emergence of the interlayer phase coherence, we analyze the dispersion relations in the limit of zero tunneling energy. We find one gapless mode with the linear dispersion relation in the CAF phase.

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SU(4)skyrmions and activation energy anomaly in bilayer quantum Hall systems

Cited by 23 publications

References 36 publications

Spin Degree of Freedom in theν=1Bilayer Electron System Investigated by Nuclear Spin Relaxation

Spin Degree of Freedom in theν=1Bilayer Electron System Investigated by Nuclear Spin Relaxation

Entanglement skyrmions in multicomponent quantum Hall systems

Goldstone Modes in Bilayer Quantum Hall Systems at ν = 2

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