PRESSURE-INDUCED Effects on the Structure of the FeSe Superconductor



Jasmine N. Millican, Daniel Phelan, Evan L. Thomas, and Juscelino B. Lećo.


Recently, superconductivity has been discovered in α-FeSe1-x (Tc = 8 K), which has a tetragonal Pb-O type structure (P4/nmm) and planar FeSe slabs that resemble the FeAs slab layers in the RO1-xFxFeAs compounds.  A polycrystalline sample of FeSe, which adopts the tetragonal PbO-type structure (P4/nmm) at room temperature, has been prepared using solid state reaction.  Transport measurements have been used to confirm the superconducting transition (Tc ≈ 8) in our polycrystalline FeSe sample.  In previous studies, the application of chemical and mechanical pressures, have been employed to increase Tc in the FeSe1-x compounds.  We have investigated pressure-induced structural changes in tetragonal FeSe at varying hydrostatic pressures up to 0.63 GPa and temperatures below (T = 50 K) and above (T = 190 K) the reported tetragonal to orthorhombic phase transition in FeSe using high resolution neutron powder diffraction.  At 50 K, which is well below the reported tetragonal to orthorhombic phase transition temperature (≈ 60 K to 80 K) for FeSe, our data are consistent with our previous findings and show a splitting of the (220) and (221) tetragonal (P4/nmm) peaks that coincides with a shift to orthorhombic symmetry (Cmme).


Presenter Name: Jasmine N. Millican

Mentor: Judith K. Stalick

Division: 610

Laboratory: NCNR

Bldg 235, Rm A113

Office: x6422

M.S.: 6102

Fax#: 301.921.9847

Sigma Xi: self (no); mentor (yes)

Category: Materials