Theorie Kolloquium | January 13, 16:30
Discrete scale invariance and non-Ginzburg-Landau criticality near quantum percolation transitions
We analyze the low-energy excitations of diluted Josephson-junctions arrays, XY-quantum antiferromagnets, and interacting bosons near the percolation threshold. We then show that the critical behavior of these systems is dramatically altered by the presence of a Berry phase that leads to an order parameter precession and, depending on the system, is caused by an external magnetic field or an external gate voltage. Most interestingly, the low energy excitations become spinless fermions with a fractal spectrum. As a result, critical properties not captured by the usual Ginzburg-Landau-Wilson description of phase transitions emerge, such as complex critical exponents, log-periodic oscillations and dynamically broken scale-invariance. [Rafael M. Fernandes, Jörg Schmalian, Phys.Rev.Lett.106, 067004 (2011)]
Prof. Dr. J. Schmalian, KIT Karlsruhe
Seminarraum Theoretische Physik
Contact: not specified