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arXiv:cond-mat/0001435

Central role of exchange-correlation hole in the 2D metal-insulator

J. S. Thakur, D. Neilson

Published Jan 31, 2000• 0 citations
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Abstract

We show that the metal to insulator transition, whether generated by decreasing the electron density or by increasing the spin alignment, is determined by a universal functional form of the two-electron correlation function g(r). This result provides direct evidence of the central role of the Coulomb repulsion and exchange in driving the metal-insulator transition.

DOI
10.48550/arxiv.cond-mat/0001435

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We show that the metal to insulator transition, whether generated by decreasing the electron density or by increasing the spin alignment, is determined by a universal functional form of the two-electron correlation function g(r). This result provides direct evidence of the central role of the Coulomb repulsion and exchange in driving the metal-insulator transition.
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This chapter focuses on studies of the critical behavior of conductivity in two-dimensional electron systems (2DES) with different amounts and types of disorder as well as different ranges of Coulomb interactions, in order to identify possible universality classes of the 2D metal-insulator transition (MIT). It discusses the manifestations of glassiness in both low- and high-disorder samples. The chapter examines the critical region near the 2D MIT in particular on describing conductivity measurements that have demonstrated dynamical scaling, the main signature of the MIT as a quantum phase transition. It also focuses on experiments that probe the nature of the insulating state, as well as charge dynamics across the MIT, in both high- and low-disorder 2DESs. There is substantial evidence that in many materials near the MIT both strong electronic correlations and disorder play an important role, and thus their competition is expected to lead to glassy behavior of electrons, in analogy with other frustrated systems.
Exact-diagonalization and quantum Monte Carlo methods are used to study the occurrence of a metal-insulator transition and the distribution of charges and magnetic moments in the ground state of a one- and two-dimensional half-filled system of correlated electrons, described by a one-band simplified Hubbard model extended with bond-charge--site-charge interactions. Numerical results for the electrical conductivity, the density of states, and the spin- and charge-density correlation functions strongly suggest that the bond-charge--site-charge interaction plays a fundamental role in the occurrence of a metal-insulator transition and of ferromagnetic order.
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Using the Fermi-liquid approach with vertex corrections, the effects of exchange and correlation are considered in a layered two-dimensional electron gas. It is shown that the interaction in the particle–hole channel can induce the metal–insulator phase transition when the Fermi momentum is comparable with the inverse interlayer spacing, pF ≈︂ /1c. The possibility of superconductivity in the region between the insulator and normal metal phases, taking into account the particle–hole excitations, is discussed. A smooth crossover from weak to strong coupling superconductivity with the decrease of the 2D carrier density is obtained. The results suggest a new way in the explanation of the phase diagram of layered high-Tc superconductors.