Observation of ortho-III correlations by neutron and hard X-ray scattering in an untwinned YBa2Cu3O6.77 single crystal

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

“…One of these, the Ortho III phase, has now been confirmed by neutron diffraction to exist at δ ≃ 0.23, for T ≤ 375K [706]. Figure 62 shows a theoretical [707] phase diagram of YBCO, along with phase boundaries determined by electron diffraction [708].…”

Mean-field and Monte Carlo calculations of the three-dimensional structure factor forYBa2Cu3Fiig1, Andersen2, Lindgård3 et al. 1996Phys. Rev. B8071View full textAdd to dashboardCite

“…23,26 However, this observation is more in line with the experimental fact that it has so far been impossible to obtain long-range ordered superstructures in YBa 2 Cu 3 O 6ϩx . 8,32 We have not undertaken a full study of the nonequilibrium behavior, but we will discuss a few results.…”

Critical chain length and superconductivity emergence in oxygen-equalized pairs ofYBa2Cu3O<

“…We believe that these spots result from domains of an orthorhombic anti-III (OIII * ) structure characterized by an ideal ...-empty-empty-full-... periodic arrangement of chains along the a direction 2 . Such a sequence gives rise to a tripling of the a axis in analogy with the ...-empty-full-full-... configuration for the ideal composition x= 2 3 of the OIII superstructure 4,8 . To our knowledge the OIII * structure is reproducibly observed around the ideal stoichiometry x= The OIII * phase cannot be justified by the original ASYNNNI model 11 , due to the neglect of long range interactions.…”

“…Its structural order drives the whole crystal structure in a variety of superstructures which have been observed [1][2][3][4][5][6][7][8] and modeled theoretically [9][10][11][12][13] in the whole compositional x-range. Beside the tetragonal (T, empty chain) and orthorhombic-I (OI, full chain) structures that characterize the end members of the compositional x-range (x=0 and 1 respectively), at least two orthorhombic modifications, ortho-II (OII) and ortho-III (OIII), occurring around the ideal x=0.5 and x=0.67 compositions and characterized by a ...-full-empty-.. and a ...-full-full-empty-... chain sequence along the a direction, are considered thermodynamically stable 8,9 . The superstructures arising from an ordering between oxygen-poor and oxygen-rich chains are well described by a simple lattice gas model, called ASYNNNI, first introduced by de Fontaine et al 11 .…”

“…Individually weighed OI and T bars were equilibrated at a given temperature (T e ) and order-stabilized at composition-dependent temperatures (T s ) within the thermal stability domain of OII and OIII superstructures 21,22 . By varying the OI/T mass ratios it is possible to prepare k-pairs in a wide range of equalized oxygen stoichiometry k. The OI (T) mass loss (gain) is due solely to a change in oxygen content in the Cu(1)O x plane 23 , and excellent agreement between calculated and experimental oxygen content at equilibrium was systematically obtained.…”