Magnetorotons and the fractional quantum Hall effect in double-quantum-well systems

The collective modes of the ν=1/2 state in double-quantum-well systems are analyzed within the framework of the single-mode approximation. The dependence of these modes on the interwell spacing is discussed. The derivation of the plasma sum rules for the two-component classical plasmas corresponding to the unpolarized [mmn] states is derived in the Appendixes.