NONLINEAR QUANTUM DYNAMICS OF STRONG VIBRATION - RELAXATION JUMPS ANDPHONON BURSTS

We examine the quantum decay of localized vibrations in an anharmonic crystal lattice. The theory which describes two-phonon anharmonic rela xation can be applied both to local modes associated with a substituti onal impurity and to intrinsic local modes (ILM) in perfect lattices. It is found that for sufficiently high initial excitations the relaxat ion of vibrations is non-exponential, it demonstrates explosion-like b ehavior at specific stages of evolution. The course of the relaxation is determined by the initial value of energy, temperature, direction o f vibrations. As an example we present the results of calculations of the relaxation of an odd local (impurity) mode in a simple cubic latti ce and discuss the influence of quantum fluctuations on the stability of the ILM in a one-dimensional monatomic chain.