Path integral Monte Carlo study of the interacting quantum double-well model: quantum phase transition and phase diagram.

The discrete time path integral Monte Carlo with a one-particle density matrix approximation is applied to study the quantum phase transition in the coupled double-well chain. To improve the convergence properties, the exact action for a single particle in a double-well potential is used to construct the many-particle action. The algorithm is applied to the interacting quantum double-well chain for which the zero-temperature phase diagram is determined. The quantum phase transition is studied via finite-size scaling, and the critical exponents are shown to be compatible with the classical two-dimensional Ising universality class--not only in the order-disorder limit (deep potential wells), but also in the displacive regime (shallow potential wells).