Superconductivity at 25 K under Hydrostatic Pressure for FeTe 0 . 5 Se 0 . 5 Superconductor

Abstract

We report the impact of hydrostatic pressure on the superconductivity and normal state resistivity of FeTe 0.5 Se 0.5 superconductor. At the ambient pressure the FeTe 0.5 Se 0.5 compound shows the superconducting transition temperature T c onset at above 13K and T c ρ=0 at 11.5K. We measure pressure dependent resistivity from 250K to 5K, which shows that the normal state resistivity increases initially for the applied pressures of up to 0.55GPa and then the same is decreased monotonically with increasing pressure of up to 1.97GPa. On the other hand the superconducting transition temperatures (T c onset and T c ρ=0 ) increase monotonically with increasing pressure. Namely the T c onset increases from 13K to 25K and T c ρ=0 from 11.5K to 20Kfor the pressures range of 0-1.97GPa. Our results suggest that superconductivity in this class of Fe-based compounds is very sensitive to pressure as the estimated pressure coefficient dT c (onset)/dP is ~ 5.8K/GPa. It may be suggested that FeTe 0.5 Se 0.5 superconductor is a strong electron correlated system. The enhancement of T c with applying pressure is mainly attributed to an increase of charge carriers at Fermi surface.

Enhancement of superconducting state properties of Fe0.994Ni0.007Te0.66Se0.34 single crystal with increasing pressure: a correlation with pressure-induced crystallinity degradation

“…The crystal structure of Fe 0.994 Ni 0.007 Te 0.66 Se 0.34 was identified as that of the anti-PbO type, but the quality was insufficient for studies of structure details. Identification of this phase is in line with the results of studies using x-ray diffraction [36,37] and other methods [38][39][40], showing that the anti-PbO phase is stable in systems of close chemical composition at pressures of up to at least ∼25 kbar. After application of pressure, the shape of diffraction spots changed: the roughly circular spots became extended along a direction corresponding to the run of Debye-Scherrer rings (figure 1), which is most likely caused by pressure-induced mosaicity increase of the sample.…”

“…The crystal structure of Fe 0.994 Ni 0.007 Te 0.66 Se 0.34 was identified as that of anti-PbO type, the quality was insufficient for studies of structure details. Identification of this phase is in line with the results of studies using X-ray diffraction [36,37] and other methods [38][39][40],…”