Fundamental physical phenomena demonstrated for the first timeIn an international first, physicists of the University of Innsbruck, Austria have experimentally observed a quantum phenomenon, where an arbitrarily weak perturbation causes atoms to build an organized structure from an initially unorganized one. The scientific team headed by Hanns-Christoph Nägerl has published a paper about quantum phase transitions in a one dimensional quantum lattice in the scientific journal Nature.With a Bose-Einstein condensate of cesium atoms, scientists at the Institute for Experimental Physics of the University of Innsbruck have created one dimensional structures in an optical lattice of laser light. In these quantum lattices or wires the single atoms are aligned next to each other with laser light preventing them from breaking ranks. Delete using an external magnetic field allows the physicists to tune the interaction between the atoms with high precision and this set-up provides an ideal laboratory system for the investigation of basic physical phenomena. "Interaction effects are much more dramatic in low-dimensional systems than in three dimensional space," explains Hanns-Christoph Nägerl. Thus, these structures are of high interest for physicists. It is difficult to study quantum wires in condensed matter, whereas ultracold quantum gases provide a versatile tunable laboratory system. And these favorable experimental conditions open up new avenues to investigate novel fundamental phenomena in solid-state or condensed matter physics such as quantum phase transitions. Quantum phase transitionThe Innsbruck physicists have observed a "pinning transition" from a superfluid ("Luttinger liquid") to an insulated phase ("Mott-insulator"). In their experiment they showed that for strongly interacting atoms an additional weak lattice potential was sufficient to pin the atoms to fixed positions along the wire ("pinning"). The atoms we ...

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