Michele Casula, Université Pierre et Marie Curie

Jeudi 7 Avril 2016 14h
Amphi Holweck, Esc C
1ème etage

Probing structural, magnetic, and superconducting properties of iron selenide (FeSe) by quantum Monte Carlo methods

In this talk we will illustrate how quantum Monte Carlo (QMC) simulations can shed light on the complex physics behind the iron based superconductors. Thanks to the computing power now available on high performance computers, it became possible to carry out many-body QMC calculations from first principles.

We will discuss our present understanding of structural, magnetic, and superconducting properties of the iron selenide (FeSe). We will address the interplay between magnetic fluctuations and structural properties in the FeSe phase diagram, as it comes out from QMC calculations.

By symmetry arguments, we demonstrate that the electronic pairing in iron-based high-temperature superconductors shows a structure which is a linear combination of planar s-wave and d-wave symmetry channels, both preserving the 3-dimensional A1g irreducible representation of the corresponding crystal point-group. We provide evidence of these general properties by performing accurate QMC ab initio calculations of the pairing function in FeSe. Our theory can rationalize and explain a series of contradictory experimental findings, such as the observation of twofold symmetry in the FeSe bulk superconducting phase, and nodeless gap in FeSe monolayer.

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