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).