Theoretical and experimental study of a quantized lattice configuration in a nearly unstable defect system

Abstract

Theoretical lattice dynamics analysis and new optical experiments on KI:${\mathrm{Ag}}^{+}$ reveal a nearly unstable low-temperature defect-host configuration, whose population decreases dramatically with temperature, but whose dynamics are consistent with a temperature-independent harmonic model involving collective motion. This behavior is in marked contrast to the temperature-dependent evolution of the dynamics of ``soft-mode'' systems.