Descripción: Institute of Physics and IOP Publishing Limited «Europhysics Letters publishes original high quality Letters in physics---short papers containing nontrivial new results, ideas, concepts, experimental methods, theoretical treatments, etc which are of broad interest and importance to one or several sections of the physics community. The presentation should satisfy the specialist, yet remain understandable to researchers in other fields through a suitable and clearly written introduction and conclusion.» ISSN 1286-4854