P-LIKE STATIONARY SELF-LOCALIZED MODES IN PURE ONE-DIMENSIONAL LATTICE WITH QUARTIC LATTICE ANHARMONICITY

A pure one-dimensional anharmonic lattice with quartic lattice anharmonicity and nearest neighbour interactions is shown to exhibit a p-like stationary self-localized mode. This is an intrinsic nonlinear mode with eigenfrequency higher than that of an s-like mode to which attention has been focussed so far. Tking the displacement differences between nearest neighbour pairs of atoms as relevant field variables leads to a much simpler formulation as compared to the case of the s-like mode. By in-troducing lattice Green's functions and using a rotating-wave approximation (RWA), analytical expressions are obtained for the eigenfrequency and eigenfuntions for a p-like mode appearing far above the harmonic frequency band. The RWA itself is also examined to show that it is a good and working approximation procedure for anhar-monic-localized-mode problems. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.