Probing the spontaneous generation of nanoscale energy localization*

A. J. Sievers

Laboratory of Atomic and Solid State Physics
Cornell University
Ithaca, New York 14853-2501

It has been realized for decades that spatially localized vibrational modes can occur in purely harmonic lattices only when disorder is introduced so that the translational invariance of the underlying lattice is removed. In recent years it has been recognized that some excitations in perfect periodic lattices which contain both nonlinearity and discreteness can localize resulting in inhomogeneous dynamical patterns, thus the study of this intrinsic localization in nonlinear periodic lattices is now under intense investigation for a variety of different physical systems. For macroscopic nonlinear systems such as Josephson junction arrays intrinsic localized modes (ILMs) have been readily observed. For condensed matter the spins in an antiferromagnetic crystal provide an experimentally accessible atomic system and here I describe our continuing investigation of the production of nanoscale localization for spin excitations. Our experimental and simulation studies show that in certain cases when the uniform mode is excited into a highly nonlinear regime it becomes modulationally unstable and breaks up into ILMs. This talk will outline the physically exciting context that is currently emerging: how macroscopic parameters such as crystal shape, DC magnetic field, and details of the E&M coupling can influence the nanoscale ILM generation process.

*Work supported by NSF-DMR and carried out in collaboration with L. English, B. Hubbard, R. Lai, and M. Sato.