title: Crystal and electronic structure of FeSe at high pressure and low temperature.
abstract: We have investigated the high-pressure crystal and electronic structures of superconducting FeSe by high-resolution synchrotron powder X-ray diffraction and density functional theory (DFT) calculations at ambient and at low temperatures down to 8 K. Ambient nuclear resonant inelastic X-ray scattering (NRIXS) experiments were performed on FeSe to understand the partial phonon density of states (PDOS) of the high-pressure phases. On the basis of our experimental results and DFT calculations, we demonstrate a pressure-induced distortion of the low-temperature Cmma phase at around 1.6 GPa and the appearance of a high-pressure Pbnm phase. Upon increasing the pressure above 9 GPa, the orthorhombic phase becomes the major phase, and a mixed-phase region exists up to 26 GPa. The pressure-induced structural changes in this system and its connection to T(c) enhancement are discussed.
authors.affiliation: Department of Physics and Astronomy and HiPSEC, University of Nevada, Las Vegas, Nevada 89154, USA. ravhi@physics.unlv.edu
authors.forename: Ravhi S
authors.initials: RS
authors.lastname: Kumar
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Stanislav
authors.initials: S
authors.lastname: Sinogeikin
authors.forename: Yuming
authors.initials: Y
authors.lastname: Xiao
authors.forename: Sathish
authors.initials: S
authors.lastname: Kumar
authors.forename: Paul
authors.initials: P
authors.lastname: Chow
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Cornelius
authors.forename: Changfeng
authors.initials: C
authors.lastname: Chen