Optical absorption in a narrow halffilled Hubbard band
Abstract
The line shape of the optical absorption spectrum in a halffilled 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