Phase diagram of the two-chain Hubbard model

TL;DR

This paper investigates the phase diagram of the two-chain Hubbard model by calculating charge and spin gaps using DMRG, revealing different behaviors in weak and strong interaction regimes and comparing results with weak coupling theories.

Contribution

The study introduces a numerical method to compute charge and spin gaps separately for symmetric and antisymmetric modes in the two-chain Hubbard model.

Findings

Different behaviors observed in weak and strong interaction regimes.

Numerical phase diagram compared with weak coupling renormalization group results.

Development of a method to calculate gaps for symmetric and antisymmetric modes.

Abstract

We have calculated the charge gap and spin gap for the two-chain Hubbard model as a function of the on-site Coulomb interaction and the interchain hopping amplitude. We used the density matrix renormalization group method and developed a method to calculate separately the gaps numerically for the symmetric and antisymmetric modes with respect to the exchange of the chain indices. We have found very different behaviors for the weak and strong interaction cases. Our calculated phase diagram is compared to the one obtained by Balents and Fisher using the weak coupling renormalization group technique.