Tunneling gap collapse and v=2 quantum Hall state in a bilayer electron system

S. J. Geer, A. G. Davies, C. H. W. Barnes, K. R. Zolleis, M. Y. Simmons, and D. A. Ritchie
Phys. Rev. B 66, 045318 – Published 24 July 2002
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Abstract

We have investigated the evolution of quantum Hall states in a GaAs-AlxGa1xAs bilayer electron system by low-temperature magnetoresistivity measurements as the system was driven from a balanced to an off-balanced configuration. At low magnetic fields, odd integer filling factor quantum Hall states were observed on balance owing to the symmetric-antisymmetric tunneling gap. However, at high magnetic fields, in the regime of tunneling gap collapse, we observed anomalous quantum Hall states at v=2 off balance and v=3 on balance. At v=2, an energy gap was present all the way from the balanced configuration to far off balance, when only one quantum well was occupied. This is attributed to a transition from a spin-polarized state on balance to a spin-singlet state off balance, either by an abrupt exchange-driven phase transition or a continuous phase transition via a series of interlayer phase coherent states.

  • Received 22 February 2002

DOI:https://doi.org/10.1103/PhysRevB.66.045318

©2002 American Physical Society

Authors & Affiliations

S. J. Geer, A. G. Davies, C. H. W. Barnes, K. R. Zolleis, M. Y. Simmons, and D. A. Ritchie

  • Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 OHE, United Kingdom

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Issue

Vol. 66, Iss. 4 — 15 July 2002

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