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