Breakdown of quantum-to-classical correspondence for diffusion in a high-temperature thermal environment

We reconsider the old problem of Brownian motion in a homogeneous high-temperature thermal environment. The semiclassical theory implies that the diffusion coefficient does not depend on whether the thermal fluctuations are correlated in space or disordered. We show that the corresponding quantum analysis exhibits a remarkable breakdown of quantum-to-classical correspondence. Explicit results are found for a tight-binding model, within the framework of an Ohmic master equation, where we distinguish between on-site and on-bond dissipators. The breakdown is second order in the inverse temperature and therefore, on the quantitative side, involves an inherent ambiguity that is related to the Ohmic approximation scheme.