Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta)

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• High-temperature superconductivity in cuprates remains a significant challenge in condensed matter physics.
• Understanding charge-transfer excitations is crucial for elucidating the electronic properties of these materials.

Purpose of the Study:

• To investigate charge-transfer excitations in HgBa(2)CuO(4+delta) using Cu-edge resonant inelastic x-ray scattering (RIXS).
• To explore the energy dependence of RIXS spectra to resolve subtle electronic excitations.

Main Methods:

• Cu-edge resonant inelastic x-ray scattering (RIXS) spectroscopy.
• Analysis of incident photon energy dependence to disentangle spectral features.
• Study of optimally doped HgBa(2)CuO(4+delta) and Mott insulator La(2)CuO(4).

Main Results:

• Resolved weakly dispersive electron-hole excitations in the 2-8 eV range.
• Identified a prominent excitation mode at 2 eV.
• Observed significant incident photon energy dependence in the RIXS spectra.

Conclusions:

• The 2 eV excitation suggests a remnant charge-transfer gap persists even in the superconducting state of HgBa(2)CuO(4+delta).
• The study highlights the importance of incident photon energy dependence in RIXS for characterizing electronic excitations.
• RIXS is a powerful tool for probing the complex electronic structure of correlated materials.