Bilayer to monolayer charge-transfer instability in semiconductor double-quantum-well structures

Disagreeing with the authors of the preceding Comment[F. A. Reboredo and C. R. Proetto, Phys. Rev. B 58, 7450 (1998)] we contend that there is no exchange-correlation driven charge-transfer instability in semiconductor double-layer systems under any circumstances. The erroneous conclusion of the preceding Comment arises from its use of a restricted mean-field approximation within the LDA self-consistent scheme, which allows an energetic comparison only between the Ising-like bilayer and monolayer states. In a generalized unrestricted approximation more exotic phases are possible because the layer index is a quantum variable. Within the Hartree-Fock scheme, we prove a theorem that the spontaneous interlayer phase coherent state, called the SP-SY phase in our original paper [Phys. Rev. B 55, 4506 (1997)], will always have a lower energy than the monolayer phase. The authors of the preceding Comment completely ignore this quantum interlayer phase coherent state. Thus any low-density layer instability in the double-quantum-well system, if it exists, will involve a transition from a bilayer to the interlayer phase coherent SP-SY state, and not to the monolayer state. The conclusion of the Comment arises from the local nature of the LDA scheme.