Pair binding and enhancement of pairing correlations in asymmetric Hubbard ladders

TL;DR

This paper investigates asymmetric two-leg Hubbard ladders using numerical methods, revealing that pairing correlations are robust against asymmetry and that these models effectively describe pairing in the crossover between charge transfer and Mott insulators.

Contribution

It introduces a detailed study of asymmetric Hubbard ladders, highlighting their robustness and providing insights into pairing mechanisms in correlated electron systems.

Findings

Pairing in symmetric ladders remains robust with asymmetry.

Asymmetric ladders are better described as two-band models.

The model captures the crossover between charge transfer and Mott insulators.

Abstract

Asymmetric two-leg Hubbard ladders with different on-site interactions $U_y$ and hoppings $t_y$ on each leg are investigated using the density matrix renormalization group method and exact diagonalizations. The pairing found in symmetric ladders is robust against the introduction of the leg asymmetry. When studying pairing, one-band Hubbard ladder models are better described as one-dimensional correlated two-band models than as sublattices of higher dimensional systems. The asymmetric Hubbard ladder provides us with a simple model for studying pairing in the crossover regime between charge transfer and Mott insulators.