Phase diagram of hole doped two-leg Cu − O ladders

Motivated by recent experiments on high-Tc cuprate superconductors pointing towards intra-unitcell order in the pseudogap phase, we investigate three distinct intra-unit-cell-ordering possibilities: nematic, nematic-spin-nematic, and current-loop order. The first two are Fermi-surface instabilities involving a spontaneous charge and magnetization imbalance between the two oxygen sites in the unit cell, respectively, while the third describes circulating currents within the unit cell. We analyze the three-band Emery model of a single CuO2 layer including various on-site and nearest-neighbor interactions within a self-consistent mean-field approach. We show how these on-site and furtherneighbor repulsions suppress or enhance particular IUC orders. In particular, we show that the attractive interactions necessary for nematic and nematic-spin-nematic orders in one-band models have their natural microscopic origin in the O-O on-site and nearest-neighbor repulsions in the three-band model. Finally, we find that while the nematic and nematic-spin-nematic orders cannot coexist in this framework, the loop-current order can coexist with nematic order.

Section: Loop Currentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mean-field analysis of intra-unit-cell order in the Emery model of the CuO2plane

Fischer

Kim

2011

“…This is certainly not the case since even from Eqs. (28,29) one can see that there are oscillations at wave vectors k F ± Q. To check that no low energy modes got missing on the way, I compare the central charge of (30) with the central charge of theory of four noninteracting fermions.…”

Section: A Derivation Of the Low Energy Field Theorymentioning

confidence: 99%

Field theory for a fermionic ladder with generic intrachain interactions

Tsvelik

2011

An effective low energy field theory is developed for a system of two chains. The main novelty of the approach is that it allows to treat generic intrachain repulsive interactions of arbitrary strength. The chains are coupled by a direct tunneling and four-fermion interactions. At low energies the individual chains are described as Luttinger liquids with an arbitrary ratio of spin vs and charge vc velocities. A judicious choice of the basis for the decoupled chains greatly simplifies the description and allows one to separate high and low energy degrees of freedom. In a direct analogy to the bulk cuprates the resulting effective field theory distinguishes between three qualitatively different regimes: (i) small doping (vc << vs), (ii) optimal doping (vs ≈ vc) and (iii) large doping (vs << vc). I discuss the excitation spectrum and derive expressions for the electron spectral function which turns out to be highly incoherent. The degree of incoherence increases when one considers an array of ladders (stripe phase).

“…27,28 Indeed for this essentially onedimensional ͑1D͒ case, various analytical tools allow one to explore the consequences of such an unusual phase. In previous work 29,30 we established that in the weak-coupling limit of Cu-O Hubbard ladders there exists a range of doping with a quasilong-range ordering of orbital currents, such that the pattern is symmetric with respect to the exchange of the two legs ͑o-OCP͒. In these studies, however, possible changes in the symmetry of the system caused by the formation of the orbital currents was not taken into account.…”

Section: Introductionmentioning

confidence: 99%

“…29,30 In the first part of this section, we recall its main characteristics, we show the condition required for the o-OCP to exist, and we also introduce relevant notations.…”

Section: Modelmentioning

confidence: 99%

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

Chudziński¹,

Gabay²,

Giamarchi³

2010

Self Cite

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.