Phonon spectra of finite dust clusters under a transverse external magnetic field

Abstract

The dynamics of two-dimensional dust clusters in plasma environment are studied at different strengths of a transverse external magnetic field, via Langevin dynamics simulation. The collective oscillation spectra obtained from simulation are compared with the dispersion relation derived from the analytical calculation under harmonic approximation. At high magnetic field strength, in the case of a linear chain, a longitudinal optic branch emerges, whereas in the case of a 2D isotropic cluster, two clear distinct branches appear, with the high frequency branch approaching cyclotron frequency. Mean squared displacement is obtained for the 2D cluster as a probe of single particle dynamics at different values of magnetization. At a larger value of coupling parameter, the cluster exhibits a crossover from normal to superdiffusive behavior with the change in the magnetic field strength, which is a result of the competition between the cyclotron and the harmonic time period. However, at a lower value of coupling parameter, the cluster remains subdiffusive at all field strengths. The study brings out several novel features of magnetized dust clusters in complex plasma environments.