Single-hole dynamics in dimerized spin liquids

Abstract

The dispersion of a single hole with spin $S=1/2$ in the $t\ensuremath{-}J$ ladder is calculated analytically. We show that the wave-function renormalization is relatively small and the quasiparticle residue of the $S=1/2$ state remains close to unity. However, at large $t/J$ there are higher spin $(S=3/2,5/2,\dots{})$ bound states of the hole with the magnetic excitations, and therefore there is a crossover from quasiparticles with $S=1/2$ to quasiparticles with higher spin.