The research activities of the group of Prof. Jörg Schmalian are in theoretical condensed matter physics. The main interest is the investigation of strongly correlated quantum mechanical many body systems, particularly their new collective behavior emerging due to competing interactions, disorder, non-equilibrium conditions or finite geometries. We are interested in understanding new materials with novel electric, optic, magnetic or thermal properties. Using quantum statistical mechanics and many-body theory, we work on phenomena such as superconductivity, quantum phase transitions, hydrodynamic transport, nano-electronics, magnetism, disordered systems and non-equilibrium dynamics.
We investigate the interplay of strong disorder and quantum fluctuations and disorder induced quantum criticality, as well as the effects of disorder on clean quantum critical points. For example, geometric criticality near a percolation transition leads to a novel universality class for the quantum phase transition in diluted Josephson-junction arrays, antiferromagnets, and interacting bosons. Most recently we demonstrated that this leads to critical properties not captured by the usual Ginzburg-Landau-Wilson description of phase transitions, such as complex critical exponents, log-periodic oscillations and dynamically broken scale invariance.