Chafic Fawaz

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A major discovery in condensed matter physics is the discovery of High-Temperature Superconductivity in cuprates (copper oxides), which still hold the record for the highest critical temperature at ambient pressure. They feature layers of CuO2 planes, believed to be responsible for their electronic properties, involving strong electronic correlations. Doping gives rise to a very complex phase diagram, going from an antiferromagnetic insulating phase to a pseudo-gap, superconductivity, and a strange metal phase, along with coexisting and/or competing orders of charge and spin. However, a comprehensive theoretical explanation of the Cooper pairing mechanism in these materials is still a debated subject, in which magnetic excitation (paramagnons) are promising candidates. The hole-doped Ca2CuO2Cl2 copper oxychloride serves as an excellent compound to investigate all these phases on common ground. Its stable and simple I4/mmm 1-layer structure and strong 2D character make it very suitable for theoretical calculations, allowing direct comparison with experimental work. In this talk I will discuss the magnetic excitation measured by Resonant Inelastic X-ray scattering (RIXS) up to the optimal doping. The paramagnon exhibits a similar dispersion with doping, along the (h,0) direction, similar to all cuprates, and a softening along the (h,h) direction, as also measured in other cuprates. Along the (h,h) direction, the bimagnon weakens in the underdoped phase, while a charge continuum seems to arise at higher doping. Raman spectroscopy confirm that the bimagnon become weaker with doping. The paramagnon band-with have the same energy as a waterfall feature in the electronic bands, as measured in Angle resolved Photo-Emission Spectroscopy (ARPES), suggesting a link between the two phenomena. This is indeed supported by cluster-DMFT calculations, which suggest a spin-polaron band emerge at such energy scale.

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Université Grenoble Alpes
0.02
Contact: Markus Grüninger / Matteo