Discrete Breathers in Condensed Matter

Abstract

Discrete breathers — non-topological spatially localized time periodic excitations — are generic solutions for lattice Hamiltonians independent of the lattice dimension. We give an introduction to the field including such aspects as spatial tail properties, lattice dimension induced energy thresholds, quantization and experimental applications. We then present recent results on breather properties in spin lattices and Josephson junction ladders. In easy plane ferromagnetic spin lattices the breather states are characterized by a local tilt of the magnetization and nonzero activation energies even in one-dimensional lattices. In Josephson junction ladders breathers lock to the external dc bias current. Variations of the current are used to generate switchings between different breather states and to probe the internal electromagnetic modes of the ladder.