Measurement of Fermi-surface distortion in double quantum wells from in-plane magnetic fields

In double quantum wells with interwell tunneling, we find that a small in-plane magnetic field substantially alters the beating observed in Shubnikov–de Haas oscillations. This phenomenon is attributed to distortion of the Fermi surface due to mixing of the symmetric and antisymmetric double-well states. The measured magnitude of the distortion is in good quantitative agreement with a calculation of the symmetric and antisymmetric mixing from the in-plane magnetic field.