DISORDER AND ORDER IN QUANTUM SYSTEMS

Ferenc Iglói (Personal webpage)

In this presentation, I will first introduce several experimental systems whose state is determined by thermal, quantum mechanical, and disorder-induced fluctuations. I will then introduce the basic model, the Ising model with random transverse fields and nearest-neighbor interactions. Its critical behavior will be investigated using the strong disorder renormalization group (SDRG) method. After the analytical treatment in one dimension, I will present numerical investigations in higher-dimensional systems. These investigations will include the calculation of critical parameters in the bulk and at the surface, as well as the scaling form of the entanglement entropy. In the second part of the presentation, I will show results for the case where relevant perturbations such as long-range forces, many-body interactions, and longitudinal fields are present.