Magnetoelastic polarons in the hole-doped quasi-one dimensional model system Y2-xCaxBaNiO5

Abstract

Charge transport in the hole-doped quasi-1D model system Y${}_{2-x}$Ca${}_x$BaNiO${}_5$ (x $leq$ 0.15) is investigated in the 50-300 K temperature range. The resistivity temperature dependence is characterized by a constant activation energy $E_a/k_{B}sim$ 1830 K at room temperature while $E_a$ decreases upon cooling. We suggest that $E_a$ measures the binding energy of the doped holes which form magneto-acoustic polarons when polarizing the neighboring Ni spins. A semi-classical model is proposed which allows to relate the electrical measurements and the bulk magnetic susceptibility. This model gives a picture of the spin-charge-lattice relation in this inhomogeneously doped quasi-1D system and explains its unusual one-particle charge excitation spectrum close to the Fermi level.

October 4th, 2004