Microscopic Current Dynamics in Nanoscale Junctions

TL;DR

This study explores the microscopic current dynamics in nanoscale quantum point contacts, revealing hydrodynamical behaviors and transient phenomena through time-dependent density-functional theory simulations.

Contribution

It introduces a combined microcanonical and time-dependent DFT approach to analyze electron flow dynamics at the nanoscale, highlighting features like nonlaminarity and edge flow.

Findings

Current flow exhibits nonlaminar and edge flow features.

Electron fluid interacts with ionic lattice and surface charges.

Quantum transport shows hydrodynamical characteristics similar to classical liquids.

Abstract

So far transport properties of nanoscale contacts have been mostly studied within the static scattering approach. The electron dynamics and the transient behavior of current flow, however, remain poorly understood. We present a numerical study of microscopic current flow dynamics in nanoscale quantum point contacts. We employ an approach that combines a microcanonical picture of transport with time-dependent density-functional theory. We carry out atomic and jellium model calculations to show that the time evolution of the current flow exhibits several noteworthy features, such as nonlaminarity and edge flow. We attribute these features to the interaction of the electron fluid with the ionic lattice, to the existence of pressure gradients in the fluid, and to the transient dynamical formation of surface charges at the nanocontact-electrode interfaces. Our results suggest that quantum transport systems exhibit hydrodynamical characteristics which resemble those of a classical liquid.