Superconducting behavior of BaTi2Bi2O and its pressure dependence

Abstract

A new superconducting sample, BaTi₂Bi₂O, was synthesized and characterized over a wide pressure range. The superconducting transition temperature, T_c, of BaTi₂Bi₂O was 4.33 K at ambient pressure. The crystal structure was tetragonal (space group of P4/mmm (No. 123)), according to the X-ray diffraction (XRD) pattern at ambient pressure. The XRD pattern was analyzed using the Le Bail method. The magnetic-field dependence of the magnetization at different temperatures was precisely investigated to elucidate the characteristics of the superconductivity. The pressure-dependent XRD patterns showed absence of structural phase transitions up to 19.8 GPa. The superconducting properties of BaTi₂Bi₂O were investigated under pressure. T_c monotonously increased with the pressure (p) up to 4.0 GPa and saturated above 4.0 GPa. The variations in the T_c–p plot were thoroughly analyzed. The Cooper pair symmetry (or superconducting pairing mechanism) was analyzed based on the magnetic field dependence of the superconductivity at ambient and high pressures, which indicated a sign of p-wave pairing for the superconductivity of BaTi₂Bi₂O, i.e., topologically nontrivial sign was suggested for BaTi₂Bi₂O.