Growth and superconductivity of single crystals La$_{1.875}$Ba$_{0.125}$CuO$_4$

The origin of high temperature superconductivity in cuprate materials is one of the biggest puzzles in material science. Since the discovery of the significant anomalous suppression of superconductivity in high temperature superconducting oxide La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) $^{[1]}$, the so-called 1/8 anomaly has been a subject of considerable research attention. Many attempts to grow the single crystals have been made, but no single crystal La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) has been successfully grown. In this work, the effects of the growth condition and the compositions of a feed rod on the crystal growth of La$_{2-x}$Ba$_{x}$CuO$_{4 }$has been studied by an infrared image floating zone method. The experimental result shows that a planar solid-liquid growing interface tends to break down into a cellular interface when the growth velocity is more than 1 mm/h. When the planar solid-liquid growing interface break down into a cellular interface, the single crystal size decreases abruptly and the as-grown rod is not single phase. The large single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) has been successfully grown. The single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) up to 8 mm diameter and 55 mm length have been cut from the as-grown bars. The superconductivity transition temperature T$_{c}$ of as-grown single crystals is 2.5 K. The static stripe order in the large single crystals has been studied by neutron scattering method$^{[2]}$. [1] A. R. Moodenbaugh \textit{et al}, Phys. Rev. B, 38(1988)4596. [2] J. M. Tranquada \textit{et al}, Nature, 429(2004)534.