Weak-coupling phase diagrams of bond-aligned and diagonal doped Hubbard ladders

TL;DR

This paper investigates the phase diagrams of bond-aligned and diagonal Hubbard ladders using perturbative renormalization group methods, revealing how doping and hopping parameters influence spin gaps and phase transitions.

Contribution

It provides new insights into how ladder orientation and hopping parameters affect the emergence of gapped phases and their relation to superconductivity.

Findings

Bond-aligned ladders exhibit a fully spin-gapped phase at low doping.

Diagonal ladders remain gapless under similar conditions.

Next-nearest-neighbor hopping influences the transition between gapped and gapless phases.

Abstract

We study, using a perturbative renormalization group technique, the phase diagrams of bond-aligned and diagonal Hubbard ladders defined as sections of a square lattice with nearest-neighbor and next-nearest-neighbor hopping. We find that for not too large hole doping and small next-nearest-neighbor hopping the bond-aligned systems exhibit a fully spin-gapped phase while the diagonal systems remain gapless. Increasing the next-nearest-neighbor hopping typically leads to a decrease of the gap in the bond-aligned ladders, and to a transition into a gapped phase in the diagonal ladders. Embedding the ladders in an antiferromagnetic environment can lead to a reduction in the extent of the gapped phases. These findings suggest a relation between the orientation of hole-rich stripes and superconductivity as observed in LSCO.