Validity of the rigid band picture for the t-J model

TL;DR

This study uses exact diagonalization to examine the doping dependence of the single particle Green's function in the t-J model, providing evidence for rigid-band behavior near half-filling and clarifying the origins of deviations from it.

Contribution

It demonstrates that the rigid-band picture is valid near half-filling in the t-J model and explains the symmetry-based reasons for deviations at higher energies.

Findings

Rigid-band behavior observed near half-filling.

Deviations due to symmetry constraints at higher energies.

No evidence for a Luttinger Fermi surface or simple nearest-neighbor hopping band.

Abstract

We present an exact diagonalization study of the doping dependence of the single particle Green's function in 16, 18 and 20 site clusters of t-J model. We find evidence for rigid-band behaviour starting from the half-filled case: upon doping, the topmost states of the quasiparticle band observed in the photoemisson spectrum at half-filling cross the chemical potential and reappear as the lowermost states of the inverse photoemission spectrum. Features in the inverse photoemission spectra which are inconsistent with rigid-band behaviour are shown to originate from the nontrivial point group symmetry of the ground state with two holes, which enforces different selection rules than at half-filling. Deviations from rigid band behaviour which lead to the formation of the `large Fermi surface' in the momentum distribution occur only at energies far from the chemical potential. A Luttinger Fermi surface and a nearest neighbor hopping band do not exist.