QUANTUM CRYSTALLIZATION OF 2-DIMENSIONAL DIPOLE SYSTEMS

An analysis is made of the region of existence of crystalline order in a system of spatially separated electrons (e) and holes (h) in two co upled quantum wells for various concentrations n, temperatures T, and distances D between the layers. A study is also made of crystallizatio n in a system of electrons in semiconductor structures near a metal el ectrode for various distances d between the semiconductor and the meta l. Calculations of the crystalline phase were made using variational c alculations of the ground-state energy of the system allowing for pair ing of quasiparticles with nonzero momentum. For a system of two coupl ed quantum wells, regions in (T,n,D) space are determined in which ele ctron (or hole) charge-density waves exist in each layer and regions w here these charge-density waves are in phase, in other words, indirect excitons (or pairs with spatially separated electrons and holes) inte racting as electric dipoles, become crystallized. In the electron syst em in semiconductor structures near a metal electrode, regions of exis tence of an electron crystal are also obtained in (T,n,D) space, where over large distances the electrons interact as electric dipoles becau se of image forces. (C) 1998 American Institute of Physics.