Coulomb-Driven Collapse of the Symmetric/Anti-symmetric Energy Gap in Double Quantum Wells at High Magnetic Fields

Abstract

Magnetotransport can directly measure the energy gap between the symmetric and antisymmetric electron states in double quantum wells (DQW). Additional quantum Hall states are observed at magnetic fields corresponding to the Fermi energy lying within the symmetric/antisymmetric (SAS) energy gap. Upon increasing the magnetic field beyond a threshold field, these quantum Hall states are absent, suggesting the collapse of the SAS energy gap in high magnetic fields. An increase of the electron density or interwell barrier thickness will destroy a larger number of quantum Hall states. Recent calculations find that coulomb interactions can drive the collapse of the SAS energy gap at high magnetic fields, in good agreement with experiment.