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|Title:||ALS-CXRO Seminar | Veronique Brouet|
|When:||03/13/2013 3:00 PM - 4:00 PM|
|Description:||ALS-CXRO Seminar Series|
Wed, March 13, 2013
Peter Fischer/Jinghua Guo
Laboratoire de Physique des Solides, CNRS-UMR8502, Université Paris-Sud, Orsay, France
ARPES investigations of iron-based superconductors
In 2008, a new family of superconductors was discovered, based on square Fe planes, with Tc up to 56K. This took the solid-state community by surprise, as Fe was not considered as a good candidate for high temperature superconductivity. Indeed, the calculated electron-phonon coupling is relatively small and the strong tendency of Fe to magnetism could appear detrimental to superconductivity. Since then, unconventional mechanisms for superconductivity and possible connections with cuprates have been actively debated.
There is a consensus that the multiband nature of iron pnictides is essential for defining their electronic properties. Many models for the superconducting and antiferromagnetic orders heavily rely on the interaction between different electron and hole Fermi Surface sheets. Angle resolved photoemission (ARPES) experiments are then very appealing in these materials, as they can in principle resolve the properties of each hole and electron bands independently.
I will show how a complete map of the electronic structure can be obtained using ARPES with different beam polarizations and photon energies. I will highlight the symmetry breaking role of the As potential on the spectral weight distribution. The role of the different orbitals will be discussed in different families, from the moderately correlated Co-doped BaFe2As2 to the strongly correlated FeTe. I will also emphasize an unusual dependence of the number of carriers on temperature, which is a direct consequence of the semi-metallic structure that has not been fully considered so far.