Spin and charge dynamics of stripes in doped Mott insulators

TL;DR

This paper investigates the spin and charge behavior of stripe phases in doped Mott insulators using a multi-flavor Hubbard model, revealing gapless collective modes and their dependence on lattice topology and doping levels.

Contribution

It introduces a solvable multi-flavor Hubbard model that captures stripe dynamics and collective excitations in doped Mott insulators, extending previous models.

Findings

Identification of gapless spin modes around specific wave vectors.

Observation of charge modes at various wave vectors.

Dependence of mode positions on lattice topology and doping.

Abstract

We study spin and charge dynamics of stripes in doped Mott insulators by considering a two-dimensional Hubbard model with N fermion flavors. For N =2 we recover the normal one-band model while for N -> infty a spin density wave mean-field solution. For all band fillings, lattice topologies and N= 4 n the model may be solved by means of Monte Carlo methods without encountering the sign problem. At N=4 and in the vicinity of the Mott insulator, the single particle density of states shows a gap. Within this gap and on rectangular topologies of sizes up to 30 X 12 we find gapless spin collective modes centered around q = (\pi \pm \epsilon_x,\pi \pm \epsilon_y) as well as charge modes centered around q = (\pm 2 \epsilon_x, \pm 2 \epsilon_y), q = (\pm \epsilon_x, \pm \epsilon_y) and q = (0,0). \epsilon_{x,y} depends on the lattice topology and doping.