Phases of the infinite U Hubbard model

TL;DR

This study uses DMRG to explore the phase diagram of the infinite U Hubbard model on ladders, revealing ferromagnetic, insulating, and unpolarized phases, with implications for 2D systems.

Contribution

The paper provides new insights into the phase behavior of the infinite U Hubbard model on ladders, identifying a novel checkerboard insulating phase at quarter filling.

Findings

Ferromagnetic Fermi liquid phase for 1 > n > 4/5

Checkerboard insulating phase at n=3/4 with bond order and antiferromagnetism

Unpolarized groundstates for 3/4 > n, suggesting similar behavior in 2D

Abstract

We apply the density matrix renormalization group (DMRG) to study the phase diagram of the infinite U Hubbard model on 2-, 4-, and 6-leg ladders. Where the results are largely insensitive to the ladder width, we consider the results representative of the 2D square lattice model. We find a fully polarized ferromagnetic Fermi liquid phase when n, the density of electrons per site, is in the range 1>n>n_F ~ 4/5. For n=3/4 we find an unexpected commensurate insulating "checkerboard" phase with coexisting bond density order with 4 sites per unit cell and block spin antiferromagnetic order with 8 sites per unit cell. For 3/4 > n, the wider ladders have unpolarized groundstates, which is suggestive that the same is true in 2D.