title: Numerical renormalization group for bosonic systems and application to the sub-ohmic spin-boson model.
abstract: We describe the generalization of Wilson's numerical renormalization group method to quantum impurity models with a bosonic bath, providing a general nonperturbative approach to bosonic impurity models which can access exponentially small energies and temperatures. As an application, we consider the spin-boson model, describing a two-level system coupled to a bosonic bath with power-law spectral density, J(omega) proportional to omega(s). We find clear evidence for a line of continuous quantum phase transitions for sub-Ohmic bath exponents 0<s<1; the line terminates in the well-known Kosterlitz-Thouless transition at s=1. Contact is made with results from perturbative renormalization group, and various other applications are outlined.
authors: Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Universität Augsburg, Augsburg, Germany.
authors: Ralf
authors: R
authors: Bulla
authors: Ning-Hua
authors: NH
authors: Tong
authors: Matthias
authors: M
authors: Vojta