Hole dynamics and photoemission in a t-J model for SrCu_2(BO_3)_2

TL;DR

This paper studies how a single hole moves in a t-J model for SrCu_2(BO_3)_2, revealing a crossover from quasiparticle to free-fermion behavior and analyzing photoemission spectra.

Contribution

It introduces a generalized spin-polaron approach to analyze hole dynamics and photoemission in a dimerized and Neel-ordered phase of the t-J model for SrCu_2(BO_3)_2.

Findings

Identifies a crossover from narrow quasiparticle band to free-fermion behavior.

Calculates the photoemission spectrum in the disordered phase.

Briefly examines hole motion in the Neel-ordered phase.

Abstract

The motion of a single hole in a t-J model for the two-dimensional spin-gap compound SrCu_2(BO_3)_2 is investigated. The undoped Heisenberg model for this system has an exact dimer eigenstate and shows a phase transition between a dimerized and a Neel phase at a certain ratio of the magnetic couplings. We calculate the photoemission spectrum in the disordered phase using a generalized spin-polaron picture. By varying the inter-dimer hopping parameters we find a cross-over between a narrow quasiparticle band regime known from other strongly correlated systems and free-fermion behavior. The hole motion in the Neel-ordered phase is also briefly considered.