Intrinsic Gap Modes in One-Dimensional Diatomic Lattices
S. A. Kiselev, S. R. Bickham and A. J. Sievers
Laboratory of Atomic and Solid State Physics and the Materials Science Center Cornell University, Ithaca, New York 14853-2501
Physical Review B, 50, 9135-52 (1994).
Brief Version

Short Abstract
Both stationary and moving intrinsic anharmonic gap modes are generated in a perfect one-dimensional diatomic chain. For the diatomic chain the even-parity anharmonic mode is unstable against conversion to an odd-parity mode while the odd-parity mode shows long term stability, in contrast with the result found earlier for a monatomic chain. Part of the mean energy of the odd-parity gap mode is associated with kinetic and potential terms of the ac vibration while the rest resides in a localized dc distortion of the lattice. Strongly localized gap modes can be approximated by the dynamics of a triatomic molecule. For larger vibrational amplitudes and associated dc distortions, the potential for the gap mode becomes double valued and the rotating wave approximation fails.

Last modified: August 10, 1997