Optical absorption in a narrow half-filled Hubbard band
Abstract
The line shape of the optical absorption spectrum in a half-filled Hubbard band is calculated to the lowest order in t/U. The problem is formulated in terms of the number of random walks of an electron and a hole which leave the spin configuration unchanged. We obtain a two particle Green's function from which both the absolute T=0 K antiferromagnetic (AF) ground state as well as a random (R) spin configuration are studied in one dimension. It is shown that at the frequency U/h the spectrum always exhibits a logarithmic singularity away from the absolute ground state. Extrapolation of the results indicates an insulator to metal transition at the critical value 4t/U=1. For the AF case, the generalization to higher dimensions is approximately done by summing all diagrams with no closed loops.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1976
- Bibcode:
- 1976PhDT........21G
- Keywords:
-
- Electromagnetic Absorption;
- Electron Transitions;
- Light Transmission;
- Spectrum Analysis;
- Antiferromagnetism;
- Electron Spin;
- Ground State;
- Random Walk;
- Spectral Line Width;
- Atomic and Molecular Physics