Signatures of Discrete Breathers in Coherent State Quantum
Discrete breathers (DBs) -- a spatial time-periodic localization of energy -- are predicted in a large variety of non-linear systems. Motivated by the conceptual bridging of the DBs phenomena in classical and quantum mechanical representation, we study their signatures in the dynamics of a quantum equivalent of a classical mechanical point in a phase space -- a coherent state. We show that in contrast to a point in a phase space that can exhibit either delocalized or localized motion, a coherent state can show signatures of a quantum equivalent of both localized and delocalized behavior. In classical mechanics, the separation between the energy regions of localized and delocalized motion is a point. In quantum mechanics, this point becomes a transient region, in which both tunneling and non-tunneling modes are present. Furthermore, the transient region contains modes that cannot be characterized as either, because the transition from non-tunneling to tunneling modes is smooth. With a further analysis we document four intriguing observations: 1. Considered as a function of coupling, the eigenstates go through avoided crossings between tunneling and non-tunneling modes. 2. The dominance of tunneling modes in high non-linearity region is compromised by an appearance of new types of modes -- high order tunneling modes. These modes are similar to the tunneling modes but have attributes of non-tunneling modes. ...