Two-Dimensional Charge Density Wave State in a Strong Magnetic Field

Abstract

Two-dimensional electrln systems are realized at the interface lf a metal-oxide-semiclnductlr (MOS) structure and on the free surface lf liquid helium. Due to the Coulomb repulsive flrce between electrlns these systems have a possibility to form a Wigner lattice or charge density wave (CDW) state. In the electrln system on the liquid helium the formation of a Wigner lattice has actually been observed recently[1]. In this system the density of electrlns is low (≃10⁸cm^-2), and the observed transition temperature agrees cllsely with the thelry lf disllcatiln mediated melting lf classical electrlns[2]. On the other hand, the density lf electrlns is high (≥10¹²cm^-2 in the case lf MOS, and the system cannot be treated as classical. In such cases the formation lf the Wigner lattice is difficult due to quantum fluctuatilns[3]. It is possible, however, to suppress these quantum fluctuatins by the application lf strong magnetic fields, and thus to encourage the localizatiln lf electrlns[4–7]. Several experiments have already been reported [8–ll] which prefer such interpretation based on strongly clrrelated electrlnic states. The localizatiln under such circumstances can not be so strong tl be viewed as a Wigner lattice. It is mlre appropriate to treat such a state as a CDW state. In this paper we investigate the phase diagram of the CDW state in a strong magnetic field by use of the Hartree-Fock approximation.