We consider a classical system of two-dimensional (2D) charged particles, interacting through a repulsive Yukawa potential $\text{exp}(-r/\lambda )/r$, and confined in a parabolic channel that limits the motion of the particles in the $y$ direction. Along the $x$ direction, the particles are subject to a periodic potential. The ground-state configurations and the normal-mode spectra of the system are obtained as a function of the periodicity and strength of the periodic potential ($V_0$) and density. An interesting set of tunable ground-state configurations are found, with first- or second-order structural transitions between them. A configuration with particles aligned, perpendicular to the $x$ direction, in each minimum of the periodic potential is obtained for $V_0$ larger than some critical value that has a power-law dependence on the density. The phonon spectrum of different configurations was also calculated. A localization of the modes into a small frequency interval is observed for sufficiently large strength of the periodic potential, and a tunable gap in the phonon spectrum is found as a function of $V_0$.

• Received 9 June 2010

DOI:https://doi.org/10.1103/PhysRevB.83.094109