Raman and X-ray diffraction studies of superconducting FeSe under pressure

• DOI: 10.1016/j.physc.2009.11.092
• Publication Date: 2009-11-16T09:39:49Z
• Authors: Tzu-Wen Huang; Chih-Ming Lin; Hwo-Shuenn Sheu; Tsu-Lien Hung; Kuo-Wei Yeh; Po-Chun Hsu; Yi-Lin Huang; Fong-Chi Hsu; Maw-Kuen Wu
• Keywords: Tetragonal crystal system; Powder Diffraction; Superconducting transition temperature

Abstract A phase transition was observed in the tetragonal FeSe superconductor under high pressure at around 2.55 GPa using X-ray scattering and Raman spectrum. From X-ray powder diffraction (XRD) experiments, the slope of the unit cell volume versus pressure curve change slightly at around 2.55–4 GPa, and the Bragg peaks of FeSe tetragonal phase disappear when the pressure reaches 11.4 GPa. We also found the superconducting transition temperature Tc increases and reaches a maximum value of ∼37 K at ∼3–4 GPa. The compressibility value ( dV / dP ) shows an abrupt change from 2.39 ( A 3 / GPa ) to 0.94 ( A 3 / GPa ) from pressure values of 0–2.55 GPa to 2.55–11.4 GPa. A similar phase transition was also observed in the Raman spectra under pressure.