Quantum Monte Carlo Study of the Hubbard Ladder

TL;DR

This paper uses quantum Monte Carlo methods to analyze the Hubbard ladder model, revealing ground state properties, excitation states, and limited hole pairing upon doping, with a focus on systems where leg hopping is small.

Contribution

It introduces a re-structuring quantum Monte Carlo method based on two-site eigenstates to study the Hubbard ladder, providing new insights into its ground and excited states.

Findings

Ground state consists of singlet-like states.

First excited state contains a triplet rung.

Limited hole pairing observed upon doping.

Abstract

We present quantum Monte Carlo results for the Hubbard model on a ladder using the re-structuring method which employ eigenstates of two-site system on a rung to construct a complete set. From technical reasons we concentrate on the case in which the hopping along the leg is much less than the hopping on the rung. We observe the ground state of the half-filled system is made of singlet-like states described in this paper and its first excited state contains one triplet rung. When the system is lightly doped states composed of an electron and a hole appear on some rungs. We find very few hole-pairing on the rung upon doping up to the quarter-filled case.