Possible hydrogen doping and enhancement of Tc (=35 K) in a LaFeAsO-based superconductor

Abstract

We report that the incorporation of hydroxide ions (OH)- significantly\nenhances the superconducting transition temperature (Tc) in the LnFeAsO-based\nsuperconductors (Ln1111: Ln = La, Ce and Pr). For La1111, Tc of the (OH)-\nincorporated sample synthesized using high-pressure technique becomes 35 K,\nwhich is higher by 7 K than the typical optimally-doped La1111 superconductors.\nSimilar enhancement in Tc is also observed for Ce1111 and Pr1111. 1H-NMR\nmeasurement have confirmed the existence of hydrogen atoms in the samples.\nAccompanying the (OH)- incorporation, the lattice parameters are largely\ncontracted, down to the values which have never been attained by any other\ndopings/substitutions.\n