Continuous transformation from spin- to pseudospin-type excitation

Sawada, A.; Terasawa, D.; Kumada, N.; Morino, M.; Tagashira, K.; Ezawa, Zyun F.; Muraki, K.; Saku, T.; Hirayama, Y.

doi:10.1016/s1386-9477(02)01040-8

Cited by 11 publications

(14 citation statements)

References 12 publications

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“…We have then calculated how the excitation energy changes as the sample is tilted. Our formula has explained quite well the activation energy anomaly found by Murphy et al 11 at the balanced point by excitations of pseudospins, and also found by Sawada et al 14 at various values of 0 by simultaneous excitations of spins and pseudospins. Though our formulas are derived for sufficiently smooth skyrmions, they have turned out to be quite good at least with the use of phenomenological values of N spin and N ppin .…”

Section: Discussionsupporting

confidence: 88%

“…It is natural that a pseudospin texture evolves into an isospin texture and then regresses to a spin texture in this process. The corresponding continuous transformation of the activation energy has already been observed experimentally by Sawada et al [13,14,15]. In this paper we explain these experimental data [11,14,15] based on the excitation of SU(4) skyrmions.…”

Section: Introductionsupporting

confidence: 69%

“…11,14,15 It seems that the exchange energy has been underestimated by making the derivative expansion. It is necessary to go beyond the present approximation to fully understand the problem.…”

Section: ͑831͒mentioning

confidence: 99%

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

Ezawa

Tsitsishvili²

2004

Phys. Rev. B

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The bilayer quantum Hall (QH) system has four energy levels in the lowest Landau level, corresponding to the layer and spin degrees of freedom. We investigate the system in the regime where all four levels are nearly degenerate and equally active. The underlying group structure is SU͑4͒. At = 1 the QH state is a chargetransferable state between the two layers and the SU͑4͒ isospin coherence develops spontaneously. Quasiparticles are isospin textures to be identified with SU͑4͒ skyrmions. The skyrmion energy consists of the Coulomb energy, the Zeeman energy and the pseudo-Zeeman energy. The Coulomb energy consists of the self-energy, the capacitance energy and the exchange energy. At the balanced point only pseudospins are excited unless the tunneling gap is too large. Then, the SU͑4͒ skyrmion evolves continuously from the pseudospin-skyrmion limit into the spin-skyrmion limit as the system is transformed from the balanced point to the monolayer point by controlling the bias voltage. Our theoretical result explains quite well the experimental data due to Murphy et al.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionsupporting

confidence: 69%

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

Ezawa

Tsitsishvili²

2004

Phys. Rev. B

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“…A Hartree-Fock calculation of the behavior of the bimeron energy in tilted magnetic field reproduces qualitatively the features found in the experiment. 11 Sawada et al 3 measured the activation energy of the 2DEG in a DQWS as a function of a parallel magnetic field and electrical bias between the layers. They define the imbalance parameter σ = (n L − n R )/(n L + n R ) where n R(L) is the density in the right(left) layer of the DQWS.…”

Section: Introductionmentioning

confidence: 99%

Pseudospin vortex-antivortex states with interwoven spin textures in double-layer quantum Hall systems

et al. 2006

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Recent experiments on strongly correlated bilayer quantum Hall systems strongly suggest that, contrary to the usual assumption, the electron spin degree of freedom is not completely frozen either in the quantum Hall or in the compressibles states that occur at filling factor ν = 1. These experiments imply that the quasiparticles at ν = 1 could have both spin and pseudospin textures i.e. they could be CP 3 skyrmions. Using a microscopic unrestricted Hartree-Fock approximation, we compute the energy of several crystal states with spin, pseudospin and mixed spin-pseudospin textures around ν = 1 as a function of interlayer separation d for different values of tunneling (∆SAS) , Zeeman (∆Z ), and bias (∆ b ) energies. We show that in some range of these parameters, crystal states involving a certain amount of spin depolarization have lower energy than the fully spin polarized crystals. We study this depolarization dependence on d, ∆SAS, ∆Z and ∆ b and discuss how it can lead to the fast NMR relaxation rate observed experimentally.

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“…The ν = 1 balanced bilayer QHS also possesses a vortex excitation; however, on account of the symmetry of the system, such an excitation becomes a pair of half-charged vortices owing to pseudospins (where a pseudospin is a layer degree of freedom). As the density imbalance of the bilayer QHS increases, it is known that the system continuously evolves to the monolayer QHS [1,2]. In earlier studies pertaining to the ν = 1 bilayer QHS, the spin degree of freedom was often neglected because of the simple assumption that a strong magnetic field leads to the generation of fully polarized spins.…”

mentioning

confidence: 99%

Spin-pseudospin intertwined excitation at the ν = 1 bilayer quantum Hall state investigated by nuclear-spin relaxation

Tsuda¹,

Terasawa²,

Nguyen³

et al. 2013

AIP Conference Proceedings

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We investigate the electron spin degree of freedom at the imbalanced density bilayer ν = 1 quantum Hall states using the resistively detected nuclear-spin-lattice relaxation rate 1/T 1 . Our measurements reveal a continuous change in 1/T 1 for σ = 1 to 0, suggesting that the balanced density ν = 1 state also exhibits electron-spin fluctuations. Moreover, the value of 1/T 1 in the back layer (the layer from which electrons are transferred to the front layer) increases at intermediate density imbalance states. This indicates that the low-energy electron-spin mode, similar to a mode observed in Skyrmion crystals, might extend across the two layers.

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Continuous transformation from spin- to pseudospin-type excitation

Cited by 11 publications

References 12 publications

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

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

Pseudospin vortex-antivortex states with interwoven spin textures in double-layer quantum Hall systems

Spin-pseudospin intertwined excitation at the ν = 1 bilayer quantum Hall state investigated by nuclear-spin relaxation

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