Pressure‐Enhanced Superconductivity in EuSr₂Bi₂S_4−xSe_xF₄ and Eu₂SrBi₂S_4−x Se_xF₄ (x = 1.5, 2)

Abstract

The dc magnetization of Se‐doped Eu2SrBi2S4−xSexF4 and EuSr2Bi2S4−xSexF4 (x = 1.5 and 2) superconductors is measured under external hydrostatic pressure. All the samples exhibit an enhanced superconducting transition temperature (Tc) upto ≈1 GPa. There is a possible crystallographic transformation by the application of pressure from a structure of low Tc to a structure corresponding to high Tc. The maximum Tc of ≈3.4 K is observed in EuSr2Bi2S2Se2F4 (positive pressure coefficient 1.08 K GPa−1). Critical current density Jc = 0.38 × 104 A cm−2 at 2 K (1 GPa) upto 0.05 T is estimated using Bean's model. EuSr2Bi2S2Se2F4 has lower critical field (Hc1) ≈100 Oe. To our knowledge, this is the first report of pressure‐dependent critical current density with application of magnetization studies in Eu‐3244‐based superconducting materials. This work devotes the effort to establish the commonality of pressure effect on the BiS2‐based superconductors, and also uncovers the importance of electron carrier density in the high‐Tc phase.

Discovery of a Superconductor Bi5O4S3Cl Containing the Unique BiS3 Layer

“…It's a medium value compared with that of BiS 2 ‐based superconductors, like PrO 0.5 F 0.5 BiS 2 (8 Oe at 2.1 K), Bi 4 O 4 S 3 (15 Oe at 2 K) and EuSr 2 Bi 2 S 2 Se 2 F 4 (≈100 Oe under 0.86 GPa at 2 K). [ 5 , 20 , 31 ]…”