Two-Hole and Four-Hole Bound States in a t-J Ladder at half-filling

TL;DR

This paper investigates the bound states in a t-J ladder at half-filling, revealing complex spectra, dispersion relations, and phase separation phenomena, especially at small t/J ratios, using linked-cluster series expansion methods.

Contribution

It provides a detailed analysis of two-hole and four-hole bound states in the t-J ladder, including their dispersion, coherence lengths, and phase separation conditions, which advances understanding of strongly correlated systems.

Findings

Bound states are prominent at small t/J ratios.

Phase separation occurs for t/J less than approximately 0.5.

Dispersion relations and coherence lengths of bound states are characterized.

Abstract

The two-hole excitation spectrum of the t-J ladder at half-filling is studied using linked-cluster series expansion methods. A rich spectrum of bound states emerges, particularly at small $t/J$. Their dispersion relations and coherence lengths are computed, along with the threshold behaviour as the bound states merge into the continuum. A class of 4-hole bound states is also studied, leading to the conclusion that phase separation occurs for $t/J \lesssim 0.5$, in agreement with other studies.