Xuejun Zhu

LAUGHLIN-LIQUID-WIGNER-SOLID TRANSITION AT HIGH DENSITY IN WIDE QUANTUM WELLS

Assuming that the phase transition between the Wigner solid and the Laughlin liquid is first-order, we compare ground-state energies to find features of the phase diagram at fixed

Metal-Insulator Transition in Solid Xenon at High Pressures

\nu

Theory of the Quasiparticle Effective Masses in Semiconductors based on an Electron Self Energy Approach

. Rather than use the Coulomb interaction, we calculate the effective interaction in a square quantum well, and fit the results to a model interaction with length parameter

Quasiparticle band structure of thirteen semiconductors and insulators

\lambda

Electronic structure and its dependence on local order for H/Si(111)-(1×1) surfaces

roughly proportional to the width of the well. We find a transition to the Wigner solid phase at high density in very wide wells, driven by the softening of the interaction at short distances, as well as the more well-known transition to the Wigner solid at low density, driven by Landau-level mixing.

Quasiparticle intepretation of photoemission spectra and optical properties of GaAs(110)

Under megabar pressures, solid h.c.p. xenon undergoes a metal-insulator transition without a concomitant structural phase transition. We have performed a first-principles quasi-particle calculation to investigate the properties of this transition resulting from the band gap closure. The theory places the transition pressure at 128 GPa. The many-body correction to the LDA band gap is found to decrease significantly as the pressure increases. This is tied with an increase of the dielectric screening.

Ab initio calculation of pressure coefficients of band gaps of silicon: Comparison of the local-density approximation and quasiparticle results.

A conceptually complete formalism for the quasiparticle effective masses in semiconductors is proposed. Our approach is based. on a generalized form of the theory, including the effects of the nonlocal, energy dependent electron self: energy operator Σ, which accounts for the electron-electron interaction. This introduces two -important effects on the expression of the effective mass: an explicit energy renormalization and an extra contribution to the matrix element that enters the usual . Our preliminary numerical results for prototypical GaAs show promising improvements over the results from the local density approximation for the calculated electron effective mass compared to experimental data.