The Anthony J Leggett Institute for Condensed Matter Special Theory Seminar, Edwin Huang (University of Notre Dame), "Direct spectroscopic observation of the Lindhard continuum"
- Sponsor
- Physics - The Anthony J Leggett Institute for Condensed Matter Theory
- Speaker
- Edwin Huang
- Contact
- Thierry Ramais
- ramais@illinois.edu
- Phone
- 217-300-2044
- Originating Calendar
- Physics - The Anthony J Leggett Institute for Condensed Matter Theory Seminar
Abstract: The charge susceptibility is one of the most fundamental objects characterizing the electronic properties of materials. In the simplest framework of Fermi-liquid theory, particle-hole excitations, encoded by the Lindhard function, form the basis for understanding the charge response and are central to screening, dissipation, and transport. Yet, despite their textbook importance, a direct spectroscopic signature of the particle–hole continuum has curiously remained unobserved. In this talk I will show how resonant inelastic x-ray scattering (RIXS) enables detection of the particle-hole continuum in the weakly correlated metal MgB2. We resolve a low-energy, linearly dispersing excitation whose velocity is comparable to the Fermi velocity, and we find quantitative agreement with simulations of the non-interacting charge susceptibility. Decomposing the simulated response identifies an intra-band origin, confirming the excitation as the Lindhard continuum. Finally, by analyzing sum rules for the charge susceptibility, we explain why orbital-selective RIXS can access particle-hole excitations whose intensity is strongly suppressed in other spectroscopies. Together, these results establish ultra-soft RIXS as a momentum-resolved probe of metallic fermiology and set a foundation for exploring elementary excitations in a broad range of quantum materials.
Zoom Link: https://illinois.zoom.us/my/icmt.seminar?pwd=ZU1KbnBLeXZLUmJKc0oyU205cDNDdz09
Meeting ID: 791 382 8328
Password: 106237