SU(4) Skyrmions and Activation Energy Anomaly in Bilayer Quantum Hall Systems

Abstract

The bilayer 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 SU(4). At $\nu =1$ the QH state is a charge-transferable state between the two layers and the SU(4) isospin coherence develops spontaneously. Quasiparticles are isospin textures to be identified with SU(4) 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 SU(4) 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. and Sawada et al. on the activation energy anomaly induced by applying parallel magnetic field.

22 pagets, 6 figures, the final version to be published in PRB

References in corpus (1)

• Simultaneous Excitation of Spins and Pseudospins in the Bilayer $\nu =1$ Quantum Hall State

Cited by in corpus (14)

• Spin Degree of Freedom in the nu =1 Bilayer Electron System Investigated via Nuclear Spin Relaxation
• Entanglement Skyrmions in multicomponent quantum Hall systems
• Quantum Hall ferromagnetism in graphene: a SU(4) bosonization approach
• Ground-State Structure in $\nu =2$ Bilayer Quantum Hall Systems
• Intrinsic gap and exciton condensation in the nu_T=1 bilayer system
• Pseudospin vortex-antivortex states with interwoven spin textures in double layer quantum Hall systems
• Collective modes of CP(3) Skyrmion crystals in quantum Hall ferromagnets
• Microscopic Theory of Skyrmions in Quantum Hall Ferromagnets
• Bilayer Quantum Hall Ferromagnet in a Periodic Potential
• The Study of Goldstone Modes in $\nu$=2 Bilayer Quantum Hall Systems
• Spin Supercurrent in the Canted Antiferromagnetic Phase
• Quantum Hall ferromagnets and transport properties of buckled Dirac materials
• Nambu-Goldstone modes and the Josephson supercurrent in the bilayer quantum Hall system
• $SU(4)$ description of bilayer skyrmion-antiskyrmion pairs