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Séminaire MCMF

Jeudi 22 janvier à 14h30,
Salle Erwin Bertaut, F418.

Oratrice : Véronique Brouet (Laboratoire de Physique des Solides d’Orsay)
"Iron pnictides as a new playground for ARPES investigations"

Abstract

In March 2008, a new family of superconductors was discovered. They are all based on square planes of Fe linked by pnictogens (As, P…) or chalcogenides (Se,Te...). It raised tremendous interest in the community because superconductivity in Fe-based compounds at such high temperatures was completely unexpected. As for the cuprates, many related compounds are magnetic, suggesting the possibility of exotic superconducting pairing through magnetic fluctuations. However, a major difference with cuprates is that Fe superconductors are multiband systems, with at least three different Fe bands crossing the Fermi level to form small hole and electron pockets. The role of correlations in this complicated electronic structure is actively debated.

Angle Resolved Photoemission is a technique of choice to image the electronic structure of a system and evaluate the strength of correlations. I will show how one can use ARPES to isolate each band of the electronic structure, define its orbital character, the renormalization of its dispersion, its 3D character and, in some cases, the behavior of the Quasiparticle lifetimes. I will underline a few unusual features that derive from the semi-metallic band structure, such as a “shrinking” of the Fermi Surface and a large temperature dependence of the number of carriers. I will show that the strength and the nature of correlations can change significantly in different families and discuss the consequences on their electronic properties.

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