Pressure-induced superconductivity in the layered pnictogen diselenide NdO0.8F0.2Sb1−xBixSe2(x=0.3and0.7)

Abstract

Polycrystalline samples of layered pnictogen (Pn) diselenide NdO0.8F0.2Sb1−xBixSe2(x=0to0.8) were successfully synthesized by solid-state reactions. Electrical resistivity in the synthesized samples systematically decreases with an increase in Bi content x, accompanied by an insulator to metal-like transition at x=0.5−0.6. Crystal structure analysis using synchrotron x-ray diffraction suggests that this transition correlates with anomalous change in c-axis length and/or distortion in Pn−Se conducting plane. Emergence of pressure-induced superconductivity was investigated using a diamond anvil cell with boron-doped diamond electrodes, employing x=0.3 and 0.7 as the representative samples. For the Sb-rich one (x=0.3), we observed a signature of superconducting transition with Tconset=5.15±0.05K at 50 GPa. The Tconset of x=0.3 increased with increasing pressure and reached 7.65 ± 0.05 K at 70.8 GPa, followed by the gradual decrease in Tc up to 90 GPa. For the Bi-rich one (x=0.7), a superconducting transition with Tconset=5.5±0.6K was induced at 43.5 GPa, which is almost comparable to that of x=0.3; besides, upper critical field (Hc2) is evaluated to be ∼10 T for x=0.7, which is higher than that of x=0.3(Hc2=6.7 T at 50 GPa).

Source-reported materials — not catalogue approval

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