[LA-SiGMA] LASiGMA Seminar - Dr. Andrey Chubukov, 3:30pm at Louisiana State University

[shelley lee]

Dear All,

 

Dr. Andrey Chubukov of the University of Wisconsin will be giving a seminar
Wednesday, October 30th,  at 3:30 pm in 1008B in the Digital Media Center at
the Louisiana State University. The title of his talk is "Pairing mechanism
and gap symmetry in Fe-based superconductors with only electron or only hole
pockets."

 

Abstract:

The pairing in moderately doped Fe-pnictides and Fe-chalcogenides is
generally understood as being due to magnetically enhanced  interaction
between hole and electron pockets. Recently, however, superconductivity has
been observed in AFe2Se2 (A = K, Rb, Cs), which contain only electron
pockets, and in KFe2As2, which contains only hole pockets. In the talk, I
review different (and sometimes conflicting) scenarios for the pairing in
these systems and propose my own.  I argue that the pairing condensate in
systems with only electron pockets necessary contains not only a
conventional intra-pocket component, but also inter-pocket component, made
of two fermions belonging to different electron pockets.  I analyze the
interplay between intra-pocket and inter-pocket pairing depending on the
ellipticity of electron pockets and the strength of their hybridization and
show that with increasing hybridization the system undergoes a transition
from a d-wave state to an s+- state, in which the gap changes sign between
hybridized pockets. This s+- state has the full gap and at the same time
supports spin resonance, in agreement with the data. Near the boundary
between d and s+- states the system develops s+id state which breaks
time-reversal symmetry.   For systems with only hole pockets, I argue for
s+- state in which the gap changes sign between hole pockets.  I show that
this state is qualitatively different from s+- state when both hole and
electron pockets are present.   I further show that the transition from one
s-wave state to the other involves highly unusual s+is state which again
breaks time reversal symmetry.

 

Biography:

Andrey Chubukov currently holds a faculty position at the University of
Wisconsin-Madison. Prior to joining UW, Dr. Chubukov was a professor at the
University of Maryland, College Park and a Research Scientist at the P.L.
Kapitza Institute for Physical Problems in Moscow, respectively. He has
authored/co-authored over 220 research papers, and has given over a 100
national and international invited and plenary conference and workshop
talks, colloquia, and seminars at various Universities and Research Centers.

 

Please note, due to technical difficulties this seminar will ONLY be
available via abobe connect. Please click on the link provided:
<http://connect.lsu.edu/la-sigma/> http://connect.lsu.edu/la-sigma/

 

UNO - Liberal Arts Building 234

LATech - PML 1015, Center for Instructional Technology, at the Wyly Tower

 

Please see attached flyer and let me know if you have any questions.

 

Regards,

Shelley Lee

Project Coordinator

225-578-0465

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