Seminar: Dynamics and Delocalization of Zhang–Rice Singlets Induced by NIR Ultrashort Pulses in Overdoped Cuprate Superconductors
- Date: 11 February 2025, 11:15–12:15
- Location: Ångström Laboratory, 92110
- Type: Seminar
- Lecturer: Fulvio Parmigiani, Department of Physics at the University of Trieste and Elettra Sincrotrone Trieste
- Organiser: Division of Materials Theory, Department of Physics and Astronomy
- Contact person: Vladislav Borisov
Cuprate superconductors, originally Mott insulators at half-filling, develop complex electronic properties upon hole doping. When a hole on the oxygen 2p-orbitals couples with a neighboring copper 3d-electron a bound state, known as Zhang–Rice Singlet (ZRS), is formed. This singlet is a quasiparticle central to both superconductivity and magnetism.
In this talk, we report time-resolved X-ray absorption spectroscopy (XAS) measurements at the oxygen K-edge on an overdoped Bi2Sr2CaCu2O8+δ (Bi2212) high quality single crystal. The experiments have been performed at the FLASH-FEL (DESY) facility.
Our data reveal that a high hole-doping leads to ZRS hybridization and the formation of a coherent band that promotes delocalized hole transport. Critically, we demonstrate that ultrashort near-infrared (NIR) pulses strongly modulate the ZRS density of states, effectively inducing dynamic changes and delocalization in the ZRS. This finding underscores the powerful role of NIR photoexcitation in tuning the balance between localized and itinerant electronic states in overdoped cuprates, providing fresh insight into the ultrafast dynamics underlying high-TC superconductivity.