The ‘classical tunnelling effect’—observations and theory

Abstract

In ground-based laboratory experiments, in experiments under microgravity conditions and in parabolic flight experiments, it is often observed that individual microparticles appear sometimes to simply pass through a strongly coupled complex plasma without affecting the fabric (the structure) of the penetrated cloud. This is surprising at first sight, because the collisional mean free path in such 'plasma crystals' is of the order of the interparticle separation. We have termed this new effect 'classical tunnelling' in analogy to its quantum mechanical counterpart. To explain this anomalous transport, a 'geometrical model for charge variation' of moving and stationary ordered particles is proposed. Theoretical predictions are in good qualitative agreement with observations and numerical simulations, and show that the phenomenon can be considered as a consequence of the non-Hamiltonian character of complex plasmas.