Charge Ordering and Phase Separations in the Spinless Fermion Model with Repulsive Intersite Interaction

Abstract

We study a simple effective model for description of charge orderings in narrow band materials, i.e. the spinless fermion model with repulsive intersite interaction W . The analysis is concentrated on the problem of phase separations and the effects of next-nearest neighbor hopping t2 on the charge ordered states in this system. The cases of d-dimensional (d ≥ 2) hypercubic lattices are considered for arbitrary particle concentration (0 < n < 1). Within the broken symmetry Hartree-Fock approximation the phase diagrams as a function of W and n are evaluated for representative cases. The results for t 2 = 0 are compared with those found for the case with nearest neighbor hopping only.

Charge Ordering and Phase Separations in the Molecular Crystal Model

“…for n e = 1 for MC model and n s = 0.5 in case of the t-W model [12], the ground state (GS) of both models for d ≥ 2 hypercubic lattices is charge ordered for any interaction strength G, W 0 > 0.…”

“…1a,b in this paper and Figs. 1a,b in [12], plotted for sq and d = ∞ lattices). The transitions at the critical value of the IP for both models are discontinuous (of the 1st order) for any n, and the critical value strongly increases with the increase of the deviation from half-filling.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] and references therein) in the field of electron charge orderings (CO) and charge density waves phenomena, due to experimental discovery of such phases in manganites, cuprates, numerous organic conductors and many other important materials. Two main mechanisms are invoked in explaining CO phenomena: electron correlations and lattice distortion.…”

“…Two main mechanisms are invoked in explaining CO phenomena: electron correlations and lattice distortion. In previous paper [12] we analyzed, in the (broken symmetry) Hartree-Fock approximation (HFA), one of the paradigmatic models of correlated electrons -the so-called t-W model of spinless fermions with repulsive interaction W . In this contribution we study a simple paradigmatic model of electron-lattice interactions -the molecular crystal (MC) model [14,15] in the static limit, and we contrast results for both models.…”

“…We have performed extensive studies of the phase diagrams and thermodynamic properties of the charge orderings in the t-W and the MC models for arbitrary particle concentration and various lattice structures, including: d = 2 square lattice, d = 3 sc lattice and the hypercubic lattice of infinite dimension (d = ∞) [15]. In this contribution we concentrate on the problem of phase separations (PS) involving CO and the effects of next--nearest-neighbor hopping (t 2 ) on the charge ordered states, which have not been studied until now for the static limit of the MC model, and compare the results with those obtained for the t-W model [12]. The case of half filled band (n e = 1) as well as the cases of arbitrary particle concentrations (0 < n e < 2) are considered.…”