$\pi$-Phase shift across stripes in a charge density wave system

TL;DR

This paper investigates the $$-phase shift phenomenon in charge density wave systems, demonstrating its generic nature across different Hubbard models through numerical simulations and charge correlation measurements.

Contribution

It shows that the $$-phase shift is a universal feature in Hubbard models, extending beyond the repulsive case to the attractive case with charge density waves.

Findings

Charge correlation measurements reveal a clear $$-phase shift.

The $$-phase shift is demonstrated in the attractive Hubbard model.

The phenomenon is shown to be generic across Hubbard models.

Abstract

Many strongly correlated materials are characterized by deeply intertwined charge and spin order. Besides their high superconducting transition temperatures, one of the central features of these complex patterns in cuprates is a phase shift which occurs across lines of decreased hole density. That is, when doped away from their AF phase, the additional charge is not distributed uniformly, but rather in `stripes'. The sublattices preferentially occupied by up and down spin are reversed across these stripes, a phenomonenon referred to as a `$\pi$-phase shift'. Many of the spin-charge patterns, including the $\pi$-phase shift, are reproduced by Density Matrix Renormalization Group and Quantum Monte Carlo calculations of simplified tight binding (repulsive Hubbard) models. In this paper we demonstrate that this sublattice reversal is generic by considering the corresponding phenomenon in the attractive Hubbard Hamiltonian, where a charge density wave phase forms at half-filling. We introduce charge stripes via an appropriate local chemical potential; measurements of charge correlation across the resulting lines of lowered density reveal a clear $\pi$ phase.