A family of exact sum rules for the one-polaron spectral function in the low-density limit is derived. An algorithm to calculate energy moments of arbitrary order of the spectral function is presented. Explicit expressions are given for the first two moments of a model with general electron-phonon interaction, and for the first four moments of the Holstein polaron. The sum rules are linked to experiments on momentum-resolved photoemission spectroscopy. The bare electronic dispersion and the electron-phonon coupling constant can be extracted from the first and second moments of the spectrum. The sum rules could serve as constraints in analytical and numerical studies of electron-phonon models.
EPL (Europhysics Letters)
- Pub Date:
- September 2002
- Polarons and electron-phonon interactions;
- Photoemission and photoelectron spectra;
- Condensed Matter - Strongly Correlated Electrons
- 4 pages