title: Perspective on the phase diagram of cuprate high-temperature superconductors.
abstract: Universal scaling laws can guide the understanding of new phenomena, and for cuprate high-temperature superconductivity the influential Uemura relation showed, early on, that the maximum critical temperature of superconductivity correlates with the density of the superfluid measured at low temperatures. Here we show that the charge content of the bonding orbitals of copper and oxygen in the ubiquitous CuO2 plane, measured with nuclear magnetic resonance, reproduces this scaling. The charge transfer of the nominal copper hole to planar oxygen sets the maximum critical temperature. A three-dimensional phase diagram in terms of the charge content at copper as well as oxygen is introduced, which has the different cuprate families sorted with respect to their maximum critical temperature. We suggest that the critical temperature could be raised substantially if one were able to synthesize materials that lead to an increased planar oxygen hole content at the expense of that of planar copper.
authors.affiliation: Institute of Experimental Physics II, University of Leipzig, Faculty of Physics and Earth Sciences, Linnéstrasse 5, Leipzig 04103, Germany.|AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, al. A. Mickiewicza 30, Krakow 30-059, Poland.
authors.forename: Damian
authors.initials: D
authors.lastname: Rybicki
authors.affiliation: Institute of Experimental Physics II, University of Leipzig, Faculty of Physics and Earth Sciences, Linnéstrasse 5, Leipzig 04103, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Jurkutat
authors.affiliation: Institute of Experimental Physics II, University of Leipzig, Faculty of Physics and Earth Sciences, Linnéstrasse 5, Leipzig 04103, Germany.
authors.forename: Steven
authors.initials: S
authors.lastname: Reichardt
authors.affiliation: AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, al. A. Mickiewicza 30, Krakow 30-059, Poland.
authors.forename: Czesław
authors.initials: C
authors.lastname: Kapusta
authors.affiliation: Institute of Experimental Physics II, University of Leipzig, Faculty of Physics and Earth Sciences, Linnéstrasse 5, Leipzig 04103, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Haase