Correlated charge-density-wave states of double-quantum-well systems in a strong magnetic field

The Hartree-Fock ground state of a double-quantum-well system in a strong magnetic field is studied as a function of the well separation. The electronic tunneling between quantum wells, which causes the symmetric-to-antisymmetric energy gap, is explicitly taken into account in the investigation. The system is found to undergo a phase transition to a new type of charge-density-wave state when the well separation d is increased beyond a certain critical value ${\mathit{d}}_{\mathit{c}}$. This phase transition is consistent with the appearance of the soft mode in the collective excitation spectrum obtained at d≊${\mathit{d}}_{\mathit{c}}$. The order parameters of the new state satisfy a sum rule similar to that of a charge-density-wave state of a two-dimensional electron system. The connection between the transition and a recent experimental result on the magnetic-field-driven destruction of integer quantum Hall states in double quantum wells is also discussed.