An exact study of lattice bosons with coupling to an ohmic bath*

In an open quantum system the presence of strong coupling between the system and its environment can result in significant changes in the behavior of the system. For instance, in the spin-boson model the coupling between the spin and a heat bath induces a quantum (quantum coherences) to classical (absence of quantum coherences) transition. While systems consisting of one or few spins have been studied in detail, less is known about equivalent many-body models. Using Path Integral Quantum Monte Carlo algorithm we are able to obtain the phase diagram of a system of two-dimensional lattice bosons with ohmic coupling to an external reservoir. We explore the role of the competition between many-body effects and dissipation in stabilizing novel quantum phases, analogous to the recently observed bose liquid phase in a dissipative one-dimensional chain of bosons [1].\\[4pt] [1] Zi Cai, Ulrich Schollw\"ock, and Lode Pollet, Phys. Rev. Lett. 113, 260403, (2014).