Many-particles systems reach an equilibrium state after sufficiently large time. These equilibrium states have been studied for long and are relatively well understood by now. However, many situations encountered in nature are far from equilibrium, and the causes may be diverse. A system can be driven out of equilibrium when it is exposed to an external perturbation such as a voltage difference, a heat flow or a particle flux. Alternatively, the system may be initially placed in a (...)
Propagation of waves in complex media is a subject of great fundamental and applied importance. Properties of light, sound, elastic or matter waves can be profoundly modified in media with broken symmetries or disorder. Studies of these properties may bring additional information about the electromagnetic vacuum, shed light on the fundamental questions in light-matter interaction, or help to improve our understanding of selected topics in condensed matter physics. On the other hand, (...)
Coherence is one of the principal features of Quantum Mechanics. It is due to coherence that matter waves can interfere and that in the quantum world the superposition of a dead and a living cat imagined by Schroedinger can in principle exist. However, phase coherence in quantum systems can be easily lost, as a result of coupling with the environment or a measuring apparatus. This is why in everyday life we do not see superpositions of a living and a dead cat, but rather cats which are (...)
Quantum gases are novel systems realized in experiments by trapping and cooling metastables atomic vapors. The gases are extremely dilute (10^9 times less than air) and reach temperatures of a few hundreds of nanoKelvins. In this regime the DeBroglie wavelength of the atoms is comparable with the inter-particle distance, and quantum mechanical aspects become evident. For bosonic isotopes, Bose Einstein condensation has been observed in 1995. For fermionic isotopes, a pairing analogous to (...)
The many-body problems is at the heart of a great variety of macroscopic condensed matter phenomena. Our activity aims at the description of generic, classical and quantum, N-body systems, ranging from electrons in solids, cold atomic gases, and quantum magnetism to the microscopic and coarse grained description of equilibrium and non-equilibrium phase transitions.
Conceptually, the easiest description is often based on mean-field approaches. Their rigorous derivations and (...)
The technological revolution of the last 30 years has been based on the continuous miniaturization of electronic and optical components. This miniaturization is rapidly reaching the point where a rich variety of quantum effects start playing a major role. Many such quantum effects are not yet well understood, and leave some fundamental questions unanswered.
In particular, one can now make low-dimensional and nanometre-sized structures from combinations of various solid-state systems, be (...)
A magnetic field has a profound effect on electron dynamics. Quasi-classically, the Lorentz force acting on the electronic charge bends the trajectories, which affects transport properties of metals and semi-conductors. One example is the appearance of an electric field perpendicular to the direction of the current flow, known as classical Hall effect. Quantum-mechanically, the electronic kinetic energy in the direction transverse to the magnetic field becomes quantized into discrete (...)