Interaction between collective modes in cuprate superconductors: Analysis of the third-harmonic response

• Applicant: Professor Dr. Götz Seibold
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564650644

The aim of the present proposal is an understanding of the third-harmonic response in cuprate superconductors with the focus on the impact of charge-density waves (CDW). This comprises an investigation of the influence of the inhomogeneous charge distribution itself but also the interplay between superconducting (SC) and CDW collective modes which then may account for the 'beating effect' observed in recent experiments on third-harmonic generation (THG). Moreover, we intend to elucidate if the CDW mode could also be responsible for the anomalous -phase jump of the third harmonic response across the resonance, i.e. when the frequency of the applied field matches the energy of the SC gap parameter. Inspired by the recent discovery of charge-density fluctuations (CDF's) in a large variety of cuprate superconductor materials we also plan to investigate a scenario, when the CDW's become short-ranged due to the imact of disorder and to compute the THG resulting from 'CDW fragments' as a model for the glassy structure resulting from CDF's. The project will be realized in close collaboration with the solid state theory group of 'La Sapienza' university in Rome, in particular with the group of Prof. Lara Benfatto, with whom we have already carried out the central preliminary work of the project. The doctoral student employed in the project will have the opportunity to increase his internationalisation skills by visiting the Roman working group.

• DFG Programme: Research Grants
• International Connection: Italy
• Cooperation Partners: Professorin Dr. Lara Benfatto; Professor Dr. Claudio Castellani