Numerically Exact Diagrammatic Approaches to Nonequilibrium Electron and Spin Transport in Molecular Junctions

Understanding electron and spin transport in molecular junctions requires theoretical tools that can treat strong correlations and nonequilibrium driving on equal footing, a task that remains challenging for most standard approaches. Recent advances in numerically exact diagrammatic quantum Monte Carlo methods, including Inchworm techniques [1, 2], have established a new paradigm for simulating interacting nanoscale systems in and out of equilibrium. In models where interactions are limited to a single orbital, these methods have enabled all-energy access to steady-state currents, spectral functions, and counting statistics in equilibrium and nonequilibrium strongly correlated regimes, opening up new ways to shape charge and spin transport using quantum correlations [3, 4]. Here, I will discuss more recent progress, which has made it possible to systematically address multi-orbital transport [5-8], paving the way toward predictive modeling of realistic molecular electronic devices.