Authors: R. Bulla, N. Tong, and M. Vojta
Journal:
Phys. Rev. Lett. 91, 170601 (2003)
We describe the generalization of Wilson's Numerical Renormalization Group method to quantum impurity models with a bosonic bath, providing a general non-perturbative approach to bosonic impurity models which can access exponentially small energies and temperatures. As an application, we consider the spin-boson model with a subohmic bath. We find clear evidence for a line of continuous quantum phase transitions for 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.