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Research & Reviews: Journal of Material Sciences | ISSN: 2321-6212 | Volulme 6
November 07-08, 2018 | Atlanta, USA
Materials Science and Engineering
15
th
International Conference and Exhibition on
Applied Crystallography
3
rd
International Conference on
&
Magnetic fluctuations in single layer FeSe
Tatsuya Shishidou
University of Wisconsin-Milwaukee, USA
S
ingle layer FeSe films grown on SrTiO
3
(001) (STO) have been an extensive focus because of their reported high
superconducting critical temperature of 40-100K. Despite a lot of work done already, the nature of the paramagnetic state
and the origin of superconductivity remains puzzling. Here we use density functional theory (DFT) spin-spiral calculations
to address the paramagnetic and superconducting nature of the monolayer FeSe/STO. The spin-spiral energy dispersion
E
(q)
is found to be extremely flat around the
q
=0 checkerboard (CB)-antiferromagnetic (AFM) configuration. Those
q
states in
the plateau share similar electronic band structure. Mapping
E
(q) onto (extended) Heisenberg models places this
S
=1 spin
system in a region of parameter space where CB-AFM quantum fluctuations lead to a magnetically disordered paramagnetic
state. Modeling the paramagnetic state as an incoherent superposition of spin-spiral states arising from thermal/quantum
fluctuations, the electronic spectrum around the Fermi level closely resembles that observed by angle-resolved photoemission
spectroscopy. A superconducting theory is developed within a symmetry-based
k.p
like method with the electrons coupled to
CB-AFM type spin fluctuations; this model provides a robust prediction of nodeless d-wave superconductivity and naturally
explains the experimental finding of fully-gapped yet anisotropic order parameter.
Biography
Tatsuya Shishidou, a native of Japan, received his Master degree in Physics (1996) from Osaka University and his PhD in Physics (1999) from Hiroshima University.
He was a Research Associate at Northwestern University, Illinois with Prof AJ Freeman from 2000 to 2003. He was an Assistant Professor at Hiroshima University
from 2003 to 2016. In 2016, he joined the University of Wisconsin-Milwaukee. He is currently an Associate Scientist working with Prof M Weinert. He is author and
co-author of over 50 scientific publications.
shishido@uwm.eduTatsuya Shishidou, Res. Rev. J Mat. Sci. 2018, Volume 6
DOI: 10.4172/2321-6212-C8-035