BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Adriana Moreo\, University of Tennessee\n\n
The discovery of high critical tem
perature superconductivity in iron-based pnictides and chalcogenides broug
ht to the \; forefront the need to develop efficient theoretical proce
dures to treat multiorbital models of interacting electrons. Among the man
y challenges\, we need to clarify the role that the orbital degree of free
dom plays in pairing and how its interaction with magnetic and lattice deg
rees of freedom leads to the stabilization of exotic phases such as the ne
matic state. Theoretical studies in the strong and weak coupling limits ca
nnot address the physically relevant intermediate regime\, with a mixture
of itinerant and localized degrees of freedom. Traditional numerical metho
ds\, such as Lanczos or quantum Monte Carlo\, have either a too rapidly gr
owing Hilbert space with increasing size or sign problems. For this reason
\, it is necessary to develop new models and techniques\, and also better
focus on systems where both experiments and accurate theory can b
e used in combination to reach a real understandingof iron pairing tendenc
ies. Examples of recent advances along these directions that will be discu
ssed in this talk include:
\ni) The development of spin-fermion model
s [1] that allow studies in the difficult nematic regime with a finite
\nshort-range antiferromagnetic correlation length above the ordering cr
itical temperatures. This type of studies
\nalso allow the inclussion
of doping\, quenched disorder\, and the study of transport and real-frequ
ency responses\;
\nii) The application of the Density Matrix Renormal
ization Group (DMRG) approach to multi-orbital Hubbard
\nmodels in ch
ain and ladder structures [2] triggered by the discovery of superconductiv
ity at high pressure in ladder
\niron-based compounds such as BaFe
\nthe recently reported [2] pairing tendencies unveiled at interme
diate Hubbard U will be discussed\;
\niii) Results for a newly develo
ped multi-orbital spin-fermion model for the CuO2 planes in hig
h Tc cuprates.[3]
\n
\n
\n \;[1] S.Liang {\\it et al.}\
, Phys.Rev.Lett.{\\bf 109}\, 047001 (2012) and Phys. Rev. Lett. {\\bf 111}
047004 (2013)\; Phys. Rev. B{\\bf 92} 104512 (2015)\; C. Bishop {\\it et
al.}\, Phys. Rev. Lett. {\\bf 117} 117201 (2016)\; Phys. Rev. B{\\bf 96} 0
35144 (2017). [2] N.D. Patel {\\it et al.}\, Phys. Rev. B{\\bf 96}\, 02452
0(2017). See also \; N.D. Patel {\\it et al.}\, Phys. Rev. B{\\bf 94}\
, 075119(2016). [3] Mostafa Hussein et al.\, in preparation.