Studies of the t-J two-leg ladder via series expansions

TL;DR

This paper uses series expansions at zero temperature to analyze the properties of the t-J two-leg ladder system at various fillings, revealing excitation spectra, bound states, and phase separation boundaries.

Contribution

It introduces a detailed series expansion approach to study the t-J ladder, including excitation spectra and phase boundaries, providing new insights into its quantum phases.

Findings

Dispersion curves for one-hole excitations are obtained.

The phase boundary between bound and unbound states is identified.

Ground state energy and phase separation line at quarter filling are estimated.

Abstract

Series expansions at T=0 are used to study properties of the half-filled $t-J$ ladder doped with one or two holes, and at quarter filling. Dispersion curves are obtained for one-hole symmetric and antisymmetric (bonding and antibonding) excitations and for the two-hole bound state. The line in the phase diagram which separates bound and unbound states is determined. For quarter filling we compute the ground state energy and estimate the location of the phase separation line. Comparisons with other numerical and analytical results are presented.