Random nonequilibrium Green's function method for large-scale quantum transport simulation

We report a random nonequilibrium Green's function method (rNEGF) to tackle the challenge of large-scale quantum transport simulation. In this method, the rNEGF is represented with Ns random superposition states of the source eigenmodes, significantly reducing the computational complexity of quantum transport properties. As a demonstration, we implement the rNEGF within the exact muffin-tin orbital-based density functional theory and calculate the electron transmission through large devices with Hamiltonian dimension up to 4×105 from first principles. It is found that a rather small Ns (even Ns=1), in orders of magnitude smaller than the number of source eigenmodes, can present reliable transmission results with a relative standard deviation ∼1%. Our calculations cover the challenging transport regimes of disorder scattering and resonant tunneling. The rNEGF method only bares the statistical error and presents an important self-averaging effect with respect to the cross-section size of the device, providing an effective stochastic quantum transport approach. © 2024 American Physical Society.