From microscopic description to statistical mechanics of CuO chain fragments in high-Tc superconductors REBa2Cu3O6+x

Evolution of lattice parameters during oxygen disordering for underdopedNdBa2Cu3OFita1, Paszkowicz2, Puźniak3 et al. 2000Phys. Rev. B2000View full textAdd to dashboardCite

“…The effect caused by a strong reduction of the intrachain oxygen interaction, as proposed in Ref. 15, was confirmed by Monte Carlo simulations in the extended ASYNNNI model of Haugerud et al 21 Most recently, a unique oxygen superstructure with 2&a ϫ2&bϫ2c unit cell was observed in NdBa 2 Cu 3 O 6.5 single crystals, using high-energy synchrotron x-ray diffraction, in the experiment performed by Frello et al 22 Despite the differences in relative variations of the lattice parameters of YBaCuO and NdBaCuO caused by oxygen rearrangement, in both cases the observed changes in the unit-cell volume follow the corresponding charge transfer between the CuO 2 and Cu-O chain planes, as will be shown in Sec. III C. Now we are going to discuss the time dependences of the lattice parameters.…”

Simple solution to problems concerning oxygen ordering inYBa2Cu3OMønster1, Lindgård2, Andersen3 1999Phys. Rev. B9170View full textAdd to dashboardCite

“…Computer modeling is needed in order to give the corresponding real-space picture. Previous model studies [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] are unable to account for a number of pertinent details recently observed in scattering experiments. Here we demonstrate that this can be achieved by Monte Carlo simulations using a simple extension of the ASYNNNI model, 14 with a fixed and limited set of interaction parameters V n .…”

“…This results in the parameters called V 1 and V 3 ; whereas V 2 also includes the covalent interaction across a Cu ion for oxygens along the chains. Detailed microscopic studies 9,[11][12][13] suggest that in particular the V 2 parameter could be dependent on the structural details such as the length of formed chains, and therefore of temperature T as well as of composition x. Including this would go beyond description possible by the simple lattice model.…”

The dependence of critical temperature on oxygen concentration in YBa2Cu3O6+x in terms of the fragmented chain model

“…The process of doping of the CuO 2 layers by holes that were created in CuO planes has been thoroughly addressed in many theoretical studies [19,20,[30][31][32][33]. It is usually explained in the frame of simple charge transfer models, that assume the degree of oxygen order in the CuO planes crucially determines the number of the holes doped [2,31,32].…”