Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Série SEM-BESSON
Domaines cond-mat
Date Lundi 18 Mai 2009
Heure 10:30
Institut IMPMC
Salle Salle de Conference, Batiment 15,140 rue de Lourmel, 75015 Paris
Nom de l'orateur Boeri
Prenom de l'orateur Lilia
Addresse email de l'orateur
Institution de l'orateur Max-Planck-Institute for Solid State Research,Heisenbergstrasse 1, Stuttgart
Titre Iron-based superconductors: what can we learn from dft?
Résumé The discovery of superconductivity with a critical temperature Tc of 26 K in fluorine-doped LaOFeAs in early 2008 has initiated a so-called "iron age" in the field of superconductivity. In a few months, several new iron-based superconductors, with Tc's as high as 55 K, have been found. Their crystal structures show a common motive, characterized by a square Fe lattice, surrounded by distorted tetrahedra of pnictogen or chalchogen atoms. Besides superconductivity, iron-based superconductors show a spin density wave (SDW) transition accompanied by a lattice distortion. This points to a possible unconventional origin of superconductivity, in analogy with the high-Tc cuprates, although there is no general consensus on the pairing mechanism. The main experimental findings concerning iron-based superconductors will be first reviewed and discussed here. Then Density Functional theory will be used to describe the electronic and vibrational properties of LaOFeAs, which is a prototype compound for iron pnictides. Using linear response calculations, I will show that the standard Migdal-Eliashberg theory fails to account for the observed critical temperature. Using an ab-initio effective tight-binding Hamiltonian, based on Fe d and As p Wannier orbitals,derived from NMTO downfolding, I will then analyze the origin of the band structure of iron pnictides, and use this tight-binding model to discuss the origin of magnetism in Fe based superconductors and its itinerant nature
Numéro de preprint arXiv
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