Comparison of different ladder models

TL;DR

This study compares the electronic properties of three ladder models (t-J, one-band Hubbard, three-band Hubbard) using DMRG calculations, highlighting differences in charge gaps and pair hopping relevant to CuO materials.

Contribution

It provides a systematic comparison of three ladder models, revealing differences in charge gaps and effective pair hoppings with implications for cuprate physics.

Findings

All models have an insulating state at one hole per Cu.

Spin gaps are similar across models for relevant parameters.

Effective pair hopping is larger in the three-band model.

Abstract

Using density matrix renormalization group calculations, we compare results obtained for the t-J, one-band Hubbard and three-band Hubbard models of a two-leg CuO ladder. Spin and charge gaps, pair binding energies, and effective pair hoppings are calculated for a wide range of parameters. All three models have an insulating state at a filling corresponding to one hole per Cu site. For physically relevant parameters their spin gaps are similar in size but they exhibit quite different charge gaps. We find that the binding energy of a pair of doped holes is of the order of the undoped ladder spin gap for all three models. The main difference between the models is the size of the effective pair hopping, which is significantly larger in the three-band model with parameters appropriate for CuO materials than in the other two models.