Collective Modes in Strongly Coupled Electronic Bilayer Liquids

We present the first reliable calculation of the collective mode structure of a strongly coupled electronic bilayer. The calculation is based on a classical model through the 3rd frequency-moment-sum rule preserving quasi-localized-charge approximation, using the recently calculated hypernetted-chain pair correlation functions. The out-of-phase spectrum shows an energy gap at $k=0\mathrm{}$ and the absence of a previously conjectured dynamical instability.