Superfluid density and microwave conductivity of FeSe superconductor

Condensed Matter Seminars

Speaker: David Broun, Department of Physics, Simon Fraser University
Date & Time: November 17, 2016 2:00 - 3:00
Location: Hennings 318
Local Contact: Doug Bonn
Intended Audience: Graduate

FeSe is an iron-based superconductor of immense current interest due to the large enhancements of Tc that occur when it is pressurized or grown as a single layer on an insulating substrate.  In collaboration with the UBC superconductivity group, we have carried out precision measurements of the superconducting electrodynamics of bulk material, at frequencies of 202 and 658 MHz and at temperatures down to 0.1 K.  The quasiparticle conductivity reveals a rapid collapse in scattering on entering the superconducting state that is strongly reminiscent of unconventional superconductors such as cuprates, organics and the heavy fermion material CeCoIn5.  At the lowest temperatures the quasiparticle mean free path exceeds 50 microns, a record for a compound superconductor, and a possible consequence of nematic order in this material.  From the superfluid response we confirm the multiband nature of superconductivity and provide strong evidence for a non-zero energy-gap minimum.  Measurements on Co-doped material provide further insight into the structure of the energy gap and place important constraints on the pairing mechanism.