Quantum information analysis of the phase diagram of the half-filled extended Hubbard model

TL;DR

This study uses quantum information entropies and the density-matrix renormalization group to analyze the phase diagram of the half-filled extended Hubbard model, revealing phase boundaries, transition orders, and new insights into phase transitions.

Contribution

It introduces an unbiased quantum information approach to determine phase boundaries and transition orders in the extended Hubbard model, providing new and independent insights.

Findings

Identification of a bond-order phase at intermediate Coulomb interaction.

Transition from charge-density-wave to other phases changes from first to second order.

Evidence for an infinite-order phase transition between spin-density-wave and bond-order phases.

Abstract

We examine the phase diagram of the half-filled one-dimensional extended Hubbard model using quantum information entropies within the density-matrix renormalization group. It is well known that there is a charge-density-wave phase at large nearest-neighbor and small on-site Coloumb repulsion and a spin-density-wave at small nearest-neighbor and large on-site Coloumb repulsion. At intermediate Coulomb interaction strength, we find an additional narrow region of a bond-order phase between these two phases. The phase transition line for the transition out of the charge-density-wave phase changes from first-order at strong coupling to second-order in a parameter regime where all three phases are present. We present evidence that the additional phase-transition line between the spin-density-wave and bond-order phases is infinite order. While these results are in agreement with recent numerical work, our study provides an independent, unbiased means of determining the phase boundaries by using quantum information analysis, yields values for the location of some of the phase boundaries that differ from those previously found, and provides insight into the limitations of numerical methods in determining phase boundaries, especially those of infinite-order transitions.