Shasta Room, Bldg 40, Room 361

2575 Sand Hill Road
Menlo Park

United States

Rudi Hackl, Walther Meissner Institut, Germany

The interaction between the electrons in a solid leads to phenomena as diverse as magnetism, density waves or superconductivity. In CuO₂ -, Fe-based or f-electron systems exhibiting different types of ordered phases in close proximity, it remains a challenge to unravel properties and origin of the interaction potential Vk,k ′. Spectroscopies such as inelastic light (Raman) scattering provide valuable information on the electronic dynamics and the interactions among the electrons. In the Fe-based superconductors results on the excitation gap and on collective (Bardasis-Schrieffer) modes afford a window into the momentum dependence of Vk,k ′. In rare-earth tritellurides the amplitude (Higgs) mode provides access to the electron-phonon coupling strength. In overdoped cuprates a new – so far unidentified – mode indicates a broken continuous symmetry at the onset of the superconducting dome. I shall present recent results with the main focus placed on new insight obtained from collective excitations in Ba₀.₆ K₀.₄ Fe₂ As₂ and ErTe₃ . The puzzling in-gap excitation in the cuprates will be addressed briefly.

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