Low energy physics
Quantum physics allows for entirely different phenomena than classical physics. Among them is collective behavior resulting from quantum mechanical coherens between particles. The individual particle sacrifice its identity for collective motion, and new types of excitations can occur. These excitations can be entirely different from the single-particle excitations themselves.
Some of the research activity in the section is focused on the study of coherent quantum effects in low-dimensional electron systems. Electrons in systems where the motion is confined to a plane can act like a quantum liquid with peculiar properties. Vortices in the liquid behave as particles with strange properties. They can be anyons, particles that are neither bosons nor fermions, and can have fractional electric charge, for instance a third of the electron charge. The quantum Hall effect is a measurable effect that one finds in a two-dimentional electron gas in a strong magnetic field and is strongly tied to this collective phenomenon. One also believes that high temperature superconductivity is caused by coherent effects in low-dimensional electron systems, but there is as of today no established theory of this phenomena. There are also one-dimensional electron systems where the electrons behave in peculiar ways.
Exotic quantum phenomena can also be found in other low dimensional systems such as in cold atomic gases trapped in electric/magnetic fields, in materials or in artifically made microelectronic devices where the electron motion is restricted. A main activity in the section is quantum mechanbical calculations, analytical and numerical, on such systems.
Quantum mechanics also gives possibilities for new ways to treat and send information. Lately this has become a very active research area internationally. In principle it is possible to construct a quantum computer that operates entirely different from a classical computer. This possibility is interesting because of the technological applications they might lead to, but also from the perspective of studying fundamental quantum mechanics from a new angle.