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

Abstract

We investigate the physical consequences of orbital current patterns ͑OCP͒ 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 ͑RG͒ analysis, we determine the changes that are caused by the SU͑2͒ spin rotational symmetry breaking which occurs when the OCP is present in the groundstate phase diagram. The most significant one is an in-plane spin-density wave 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 SU͑2͒ symmetry breaking underscores the specificity of the OCP-induced effects.

Loop currents in two-leg ladder cuprates

“…At variance, other patterns with a set of four LCs (Fig. 6c usually referred to as CC-θ I phase) [18][19][20] give rise to different magnetic scattering selection rules that do not satisfy the measured structure factor with extinctions at Bragg positions where the observed intensities are maximum.…”

“…For both samples and although the magnetic cross section is larger than in superconducting cuprates, the LCs magnetic moment is of the same order of magnitude 1,3-5 due to 1 . c LC state CC-θ I 18,19 . d LC state CC-θ II 8 showing two possible patterns breaking rotational symmetry along the diagonals.…”

“…Beyond conventional spin magnetism, a new form of magnetism may originate from magneto-electric loop currents (LCs) [7][8][9][10][11][12][13] or Dirac multipoles [14][15][16][17] . While most of these states are usually discussed for hole-doped quasi-2D transition metal oxides such as cuprates and iridates, the existence of LCs was also addressed in quasi-1D spin ladder cuprates [18][19][20] . Sr 14 − x Ca x Cu 24 O 41 is a prototype twoleg ladder system whose hole doping can be tuned by Ca for Sr substitution.…”

“…This study is motivated by the recent theoretical proposal that spin liquids and topological order could be dressed with ancillary phases, such as LCs, that highlight their intrinsic nature [10][11][12] . It represents a promising candidate for LCs hunting in the context of low-dimensional spin liquids [18][19][20] .…”

Electron scattering from domain walls in ferromagnetic Luttinger liquids

“…A diagonal equation in the φ i 's is not recovered and to perform any further analysis we would have to re-diagonalize the problem and then renormalize the model once again, repeating these steps until we reached the fixed point. 37 This is perhaps not totally unexpected as the scattering terms we are dealing with explicitly couple the normal modes. We leave the more involved second order RG analysis to a future work and focus here on what the first order equations can tell us.…”