Conductance Modulation in Double Quantum Wells Due to Magnetic Field-Induced Anticrossing

We observe a strong modulation of the low temperature in-plane conductance $G_{\parallel }$ of coupled quantum wells (QW's) by an in-plane magnetic field $B_{\parallel }$ and attribute this to an anticrossing of the two QW dispersion curves. The anticrossing produces a partial energy gap, yielding large, $B_{\parallel }$-tunable distortions in the Fermi surface and density of states. Sweeping $B_{\parallel }$ moves the energy gap through the Fermi level, with the upper and lower gap edges producing a sharp maximum and minimum in $G_{\parallel }$, in agreement with theoretical calculations. The gap energy is directly determined from the data.