Crystal growth and doping control of HgBa2CuO4+δ, the model compound for high-Tc superconductors. (October 2019) - Legros, A.
Graphical abstract: With only one CuO2 plane per tetragonal unit cell and the highest T C value of all single-layer cuprates, the superconducting HgBa2 CuO4+ δ is an ideal candidate to clarify the relationship between the crystallographic structure and the electronic properties, and improve the comprehension of high- T C superconductivity mechanisms so as to reach still higher T C values. Here we propose an original procedure for the elaboration of very high quality single crystals, which allows a fine tuning of the oxygen content so as to probe the phase diagram of cuprates in a large range of composition. Highlights: Crystal growth, doping control of the model compound for high-Tc superconductors. New method to grow high quality single crystals of high-Tc HgBa2 CuO4+ δ superconductor. Single crystals with surfaces of high optical quality. Fine control of the oxygen content and superconductivity of crystals. Single crystal X-ray diffraction data for different doping levels. Abstract: A self-flux method to grow very high quality single crystals of the superconducting HgBa2 CuO4+δ mercury cuprates is reported. The single crystals are platelet-shaped, with surfaces of high optical quality and good crystallographic properties. Annealing enables optimization of TC up to TC max = 94 K. With adequate treatment, the doping level of the crystalline samples can be finely controlled in a wide under- and over-doped range. Preliminary structural characterization from single crystal X-ray diffraction data is given for different doping levels. The signature of under- and over-doping for both pure and gold-substituted crystals has been identified from micro-Raman spectroscopy measurements.