Effect of Fluorination on the Structure and Superconducting Properties of the Hg-1201 Phase

Atomic ordering of the fluorine dopant in theHgBa2CuO4+δhigh-TcCorreia1, Haas2, Amaral3 et al. 2005Phys. Rev. B81130View full textAdd to dashboardCite

“…Contrary to the results quoted in Ref. 11 we find theoretically a stronger shift in the O͑2͒ position for O ␦ than for F ␦ doping by a factor of 2, as might be expected from a simple charge doping model. The present calculations also result in strongly different z coordinates for the nonequivalent Ba sites in each supercell, in particular.…”

“…Figure 5 shows the calculated individual internal position parameters z for the apical oxygen, O͑2͒, and the Ba sites as a function of ␦F, plotted together with the measured average parameters. 11 The experimental values for the undoped, ␦F = ␦O = 0, case were obtained by extrapolation of more recent results. 23 The calculations reproduce the measured trends, though no fully quantitative agreement is obtained.…”

“…The lower Q value could possibly be explained by an extra elongation of the average mercury-apical oxygen bond distance, d͓O͑2͒-Hg͔, upon fluorine doping, as observed in neutron diffraction data. 11 In Fig. 1͑d͒ after the third annealing step under argon, the amplitude of the spectrum is slightly reduced.…”

“…More recently, comparative studies of fluorine ͑F − ␦ ͒ and oxygen ͑O 2− ␦ ͒ doping in high quality Hg1201 samples have been performed. 11 These works have shown that, on one hand, the effective injection of holes into the Cu planes is proportional to the dopant nominal charges, as expected from a simple ionic doping model, but, on the other hand, the doping efficiency has remained well below the value expected from the excess fluorine F ␦ concentration in a similar and unexplained way as for O ␦ . Hence, the simple idea that the effective hole count in the Cu planes is just given by the dopant concentrations and ionic charges remains questionable.…”

Synchrotron x-ray scattering study of charge-density-wave order in HgBa2CuO4+δ

“…All cuprates exhibit inherent inhomogeneity and disorder [23,24], and Hg1201 is no exception in this regard [25,26]. In particular, the interstitial oxygen atoms in underdoped samples are likely randomly distributed in the HgO δ layer (δ ≈ 0.18 at optimal doping) [27][28][29], yet the quasiparticle [12,42]. Solid blue line: Doping dependence of the superconducting (SC) transition temperature T c (p) [43].…”