Spin rotational symmetry breaking by orbital current patterns in two-leg ladders.

TL;DR

This paper explores how orbital current patterns in doped two-leg Cu-O ladders break spin rotational symmetry, leading to measurable magnetic signatures and a new in-plane SDW gap, with implications for experimental detection.

Contribution

It provides a detailed analysis of the effects of orbital current patterns on symmetry breaking, magnetic properties, and conductance in two-leg ladders, including experimental signatures.

Findings

Orbital current patterns produce detectable magnetic fields.

SU(2) symmetry breaking induces an in-plane SDW gap.

Conductance is affected by impurity scattering in the presence of OCP.

Abstract

We investigate the physical consequences of orbital current patterns (OCP) in doped two-leg Cu-O Hubbard ladders. The internal symmetry of the pattern, in the case of the ladder structure, differs slightly from that suggested so far for cuprates. We focus on this OCP and look for measurable signatures of its existence. We compute the magnetic field produced by the OCP at each lattice site, and estimate its value in view of a possible experimental detection. Using a renormalization group (RG) analysis, we determine the changes that are caused by the SU(2) spin-rotational symmetry breaking which occurs when the OCP is present in the ground state phase diagram. The most signifcant one is an in-plane SDW gap opening in an otherwise critical phase, at intermediate dopings. We estimate the value of this gap, give an analytic expression for the correlation functions and examine some of the magnetic properties of this new phase which can be revealed in measurements. We compute the conductance in the presence of a single impurity, using an RG analysis. A discussion of the various sources of SU(2) symmetry breaking underscores the specificity of the OCP induced effects.