Many-body effects on the symmetric-antisymmetric gap in double quantum wells in strong magnetic fields

We study the effect of the electron-electron interaction on the symmetric-antisymmetric energy gap in double quantum well systems in strong magnetic field at total filling factor ν=1. We sum self-energy diagrams up to second order, and also we evaluate the self-energy in the GWΓ approximation. We find that in the GWΓ approximation the symmetric-antisymmetric energy gap collapses when the charge-density excitation develops a soft mode. Then the charge-density wave instability, which occurs in the double quantum well system at ν=1, is accompanied by a transition to a metallic system.