Effect of Hydrostatic Pressure on Eu3−xSrxBi2S4−ySeyF4 (x = 1 and 2 and y = 1.5 and 2) Superconductors

We have investigated the effect of pressure on Se-doped Eu2SrBi2S4F4 and EuSr2Bi2S4F4 at S sites. We report the electrical resistivity measurements under hydrostatic pressure (P) ~ 3 GPa and ~ 2.5 GPa on Eu2SrBi2S4−ySeyF4 [dTc/dP ~ 1.68 K/GPa (x = 2)] and EuSr2Bi2S4−xSexF4 [dTc/dP ~ 1.57 K/GPa (x = 1.5) and 1.74 K/GPa (x = 2)] respectively. Pressure-induced superconductivity has been observed in EuSr2Bi2S2.5Se1.5F4 with Tc of 2.42 K at 0.12 GPa and the Tc increases with further application of P up to 3 GPa (dTc/dP ~ 1.12 K/GPa) and maximum Tc of ~ 8 K is observed for EuSr2Bi2S2Se2F4. These results corroborate the behavior of this material under high pressure magnetization studies. Further, the metallic nature is observed for EuSr2Bi2S2.5Se1.5F4, EuSr2Bi2S2Se2F4, and Eu2SrBi2S2Se2F4 compositions and it is slightly suppressed with the application of pressure. Pressure effect on upper critical field Hc2(0) is estimated from magnetic field–dependent ρ(T) measurements and it is found to be higher for all compositions than parent compound. The field-dependent thermal activation energy (μ0/kB) is calculated from Arrhenius plot using ρ(T) and designates a robust flux pinning potential which might be co-existing with applied magnetic field and pressure.