title: High-pressure studies onTcand crystal structure of iron chalcogenide superconductors.
abstract: The superconducting transition temperature,Tc, in iron-based solids can be enhanced by applied pressure:Tcincreases from 8 to 37 K for the 11-type FeSe when the pressure is raised from 0 to 4 GPa. High-pressure studies can elucidate the mechanism of superconductivity in such novel materials. In this paper, we present a high-pressure study of Fe(Se1-xTex) and Fe(Se1-xSx). In the case of Fe(Se1-xTex), the maximumTcunder high pressure did not exceed theTcof FeSe, which can be attributed to the structural transition to the monoclinic phase. For Fe(Se1-xSx) (0 <x< 0.3),Tcexhibited a significant increase with pressure; however, the maximumTcunder high pressure did not exceed theTcof FeSe. This may be due to the disorder induced by substituting S for Se, which is similar to the pressure effect onTcfor the 1111-type superconductor Ca(Fe1-xCox)AsF. TheTcof Fe(Se1-xSx) showed a complex behavior below 1 GPa, first decreasing and then increasing with increasing pressure. From high-pressure x-ray diffraction measurements, theTc(P) curve was correlated with the local structural parameter.
authors.affiliation: College of Humanities and Sciences, Nihon University, Setagaya, Tokyo 156-8550, Japan; Transformative Research-Project on Iron Pnictides (TRIP), Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: College of Humanities and Sciences, Nihon University, Setagaya, Tokyo 156-8550, Japan; Transformative Research-Project on Iron Pnictides (TRIP), Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tomita
authors.affiliation: College of Humanities and Sciences, Nihon University, Setagaya, Tokyo 156-8550, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Tokyo Metropolitan University, 1-1 Minami-Osawa, Hajioji, Tokyo 192-0397, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Mizuguchi
authors.affiliation: Transformative Research-Project on Iron Pnictides (TRIP), Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075, Japan; Nano Frontier Materials Group, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Takano
authors.affiliation: Ultra-High Pressure Processes Group, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakano
authors.affiliation: Institute for Solid State Physics (ISSP),University of Tokyo, Kashiwa 277-8581, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Matsubayashi
authors.affiliation: Institute for Solid State Physics (ISSP),University of Tokyo, Kashiwa 277-8581, Japan.
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Uwatoko
keywords: Fe(Se1−xSx); Fe(Se1−xTex); crystal structure; pressure effect; superconductivity