K. Pedersen, J.^{2}; V. Fedorov, D.^{2}; S. Jensen, A.^{2}; Zinner, Nikolaj Thomas^{2}

Affiliations:

^{1} Department of Physics and Astronomy, Science and Technology, Aarhus University^{2} Department of Physics and Astronomy, Science and Technology, Aarhus University

DOI:

10.1088/0953-4075/47/16/165103

Abstract:

We consider crystal formation of particles with dipole-dipole interactions that are confined to move in a one-dimensional helical geometry with their dipole moments oriented along the symmetry axis of the confining helix. The stable classical lowest energy configurations are found to be chain structures for a large range of pitch-to-radius ratios for relatively low density of dipoles and a moderate total number of particles. The classical normal mode spectra support the chain interpretation both through structure and the distinct degeneracies depending discretely on the number of dipoles per revolution. A larger total number of dipoles leads to a clusterization where the dipolar chains move closer to each other. This implies a change in the local density and the emergence of two length scales, one for the cluster size and one for the inter-cluster distance along the helix. Starting from three dipoles per revolution, this implies a breaking of the initial periodicity to form a cluster of two chains close together and a third chain removed from the cluster. This is driven by the competition between in-chain and out-of-chain interactions, or alternatively the side-by-side repulsion and the head-to-tail attraction in the system. The speed of sound propagates along the chains. It is independent of the number of chains although depending on geometry.

Type:

Journal article

Language:

English

Published in:

Journal of Physics B: Atomic, Molecular and Optical Physics, 2014, Vol 47, Issue 16