Observation of extreme field-induced mass deviations in double quantum wells.

Abstract

Large deviations are measured in the cyclotron effective mass ${\mathit{m}}_{\mathit{c}}$ near the recently observed partial energy gap arising in strongly coupled GaAs double quantum wells (QW's) subject to in-plane magnetic fields ${\mathit{B}}_{\mathrm{\ensuremath{\parallel}}}$. The energy gap results from an anticrossing of the two QW dispersion curves, shifted in k space relative to one another by ${\mathit{B}}_{\mathrm{\ensuremath{\parallel}}}$. The severely distorted dispersion near the gap yields an ${\mathit{m}}_{\mathit{c}}$ repressed by more than a factor of 3 near the upper gap edge, and enhanced by \ensuremath{\sim}50% near the lower gap edge. The data show excellent agreement with recent theoretical calculations.