High-temperature superconductivity (T _c onset at 34 K) in the high-pressure orthorhombic phase of FeSe

Abstract

We have studied the structural and superconducting properties of β-FeSe under pressures up to 26 GPa using synchrotron radiation and diamond anvil cells. The bulk modulus of the tetragonal phase is 28.5(3) GPa, much smaller than the rest of Fe based superconductors. At 12 GPa we observe a phase transition from the tetragonal to an orthorhombic symmetry. The high-pressure orthorhombic phase has a higher Tc reaching 34 K at 22 GPa.

Pulsed laser deposition conditions and superconductivity of FeSe thin films

“…In applying this pressure, both a-and c-axis values decreased and the transition of the crystal structure from tetragonal to orthorhombic was observed at room temperature. The pressure dependence of T c showed a jump at the structural transition [25], indicating the importance of the crystal structure. With this bulk crystal perspective in mind, in thin films, Yeh et al observed a structural transition from tetragonal to triclinic at 105 K [9].…”

“…reported that superconducting FeSe undergoes a structural transition from tetragonal to orthorhombic at 90 K but that non-superconducting FeSe does not undergo this transition [23]. With pressure, the T c of FeSe increased to 34 K [24,25]. In applying this pressure, both a-and c-axis values decreased and the transition of the crystal structure from tetragonal to orthorhombic was observed at room temperature.…”

Synthesis and physical properties of FeSe1/2Te1/2 superconductor

“…The lattice parameters are in good agreement with previously reported literature. 11,16 The magnetic susceptibility at 10 Oe is shown in Fig. 2 for both zero-field cooling ͑ZFC͒ and field cooling ͑FC͒ measuring conditions.…”

“…Very high dT c / dP of FeSe warrants large scope for increasing its T c by chemical pressure through on site substitutions. Garbarino et al 16 found that under compression, FeSe transforms from the original tetragonal structure to an orthorhombic high pressure phase above 12 GPa. The high-pressure orthorhombic phase has a higher T c reaching 34 K at 22 GPa.…”

Dynamic critical curve of a synthetic antiferromagnet

“…The superconducting transition temperature of the end member, FeSe ͑T c Ϸ 8 K͒, whose superconductivity was first discovered by Hsu et al, 7 can be raised to 14-15 K by partial Te substitution for Se, 8,9 and up to ϳ27-37 K by applying hydrostatic pressure. [10][11][12][13] Densityfunctional theory ͑DFT͒ calculations showed that Fermi surfaces ͑FS͒ of FeSe and FeTe are similar to those of FeAs compounds, 14 which was confirmed by recent photoemission studies. 15 Superconductivity in Fe 1+y Se is extremely sensitive to stoichiometry 16 and cannot be understood in the standard electron-phonon picture.…”