Current-Induced Forces for Nonadiabatic Molecular Dynamics

Abstract

We present general first principles derivation of expression for current-induced forces. The expression is applicable in non-equilibrium molecular systems with arbitrary intra-molecular interactions and for any electron-nuclei coupling. It provides a controlled consistent way to account for quantum effects of nuclear motion, accounts for electronic non-Markov character of the friction tensor, and opens way to treatments beyond strictly adiabatic approximation. We show connection of the expression with previous studies, and discuss effective ways to evaluate the friction tensor.

Electronic friction in interacting systems

“…we are in regime where bath induced correlations between many-body eigenstates of the system become less important). Relative accuracy of the generalized Head-Gordon and Tully expression in the case of weak system-bath interaction was demonstrated in our previous study [40] for a non-interacting model. As we showed in that study, nonequilibrium generalization of the Head-Gordon and Tully result comes from S 1 = S 3 and S 2 = S 4 subset of terms in the general expression (17).…”

“…We compare the Hubbard NEGF wit the mean-field standard NEGF treatment of Ref. [25] and with the nonequilibirum generalization [40] of the Head-Gordon and Tully expression [46]. As expected standard and Hubbard NEGF results coincide in non-and weakly interacting systems, while for strong intra-system interactions (coupling between molecular exciton and cavity mode) the mean-field treatment fails qualitatively.…”

“…Such systems have been realized experimentally; however, so far measurements were restricted to unbiased junctions. Recently, we derived general expression for electronic friction in interacting systems [40]. We showed that the friction can be conveniently expressed in terms of retarded projection of the single-particle Hubbard Green function.…”

“…) excites (destroys) quanta in the cavity mode and mode α of the radiation field. Note that HamiltonianĤ vib representing vibrational degrees of freedom and their coupling to electronic degrees of freedom is only used to derive expression for the electronic friction (see Ref [40]. for details) and does not participate in…”

Electron Transfer Methods in Open Systems

“…Thus, perturbative expansion in the system-baths couplings in each order yields product of two multi-time correlation functions: one for the system and one for the . The technique appears to be quite stable over wide range of parameters, 69 helpful in evaluation of electronic friction in junctions, 70,71 and useful as a convenient tool in first principles simulations of optoelectronic devices. [56][57][58] It is important to realize, however, that requirement of equilibrium character of the…”