University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Wednesday, October 30th 2019
Speaker: Peter D. Johnson, CM Physics and Materials Science Division, BNL
Subject: Time Reversal Symmetry Breaking in the FeTe1-xSex family of high Tc superconductors

Laser-based ARPES with variable light polarization offers a powerful probe of the electronic structure near the center of the Brillouin zone. Here the technique is used to examine the Fe-based superconductor family, FeTe1-xSex. At the zone center we observe the presence of Dirac cones with helical spin structure as expected for topological surface states and as previously reported in the related FeTe0.55Se0.45.[1] These studies are compared with theoretical studies that take account of the disordered local magnetic moments related to the paramagnetism observed in this system. Indeed including the magnetic contributions in the theoretical description is necessary to bring the chemical potential of the calculated electronic band structure into alignment with experimental observation. In the bulk superconducting state for FeTe0.7Se0.3 the system appears to reflect the presence of some level of orbital selectivity in the pairing even though no structural transition occurs at the transition temperature Tc. At the same time the topological state appears to acquire mass below Tc.

[1] P. Zhang et al., Science 360, 182 (2018)

Faculty Host: Martin Greven

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