Effects of quantum recoil forces in resistive switching in memristors

Memristive devices, whose resistance can be controlled by applying a voltage and further retained, are attractive as possible circuit elements for neuromorphic computing. This new type of devices poses a number of both technological and theoretical challenges. Even the physics of the key process of resistive switching, usually associated with formation or breakage of conductive filaments in the memristor, is not completely understood yet. This work proposes a new resistive switching mechanism, which should be important in the thin-filament regime and take place due to the back reaction, or recoil, of quantum charge carriers, independent of the conventional electrostatically-driven ion migration. Since thinnest conductive filaments are in question, which are only several atoms thick and allow for a quasi-ballistic, quantized conductance, we use a mean-field theory and the framework of nonequilibrium Green's functions to discuss the electron recoil effect for a quantum current through a nanofilament on its geometry and compare it with the transmission probability of charge carriers. Namely, we first study an analytically tractable toy model of a 1D atomic chain, to qualitatively demonstrate the importance of the charge-carrier recoil, and further proceed with a realistic molecular-dynamics simulation of the recoil-driven ion migration along a copper filament and the resulting resistive switching. The results obtained are expected to add to the understanding of resistive switching mechanisms at the nanoscale and to help downscale high-retention memristive devices.