Transport of electrons in a single molecule junction is the simplest problem general subject area molecular electronics. In past few years, this has been extended to probe beyond simple tunnelling associated with large energy gaps between electrode Fermi level and levels, deal smaller gaps, near-resonance and, particularly, effects due interaction electronic vibrational degrees freedom. This overview devoted theoretical computational approaches that have taken understanding transport...

Much current experimental research on transport in molecular junctions focuses finite voltages, where substantial polarization-induced nonlinearities may result technologically relevant device-type responses. Because molecules have strong polarization responses to changing charge state or external field, isolated between electrodes can show strongly nonlinear current-voltage For small applied voltages (up ∼0.3 volt), weak interaction transporting electrons and vibrations provides the basis...

We study inelastic electron tunneling through a molecular junction using the nonequilibrium Green's function formalism. The effect of mutual influence between phonon and subsystems on process is considered within general self-consistent scheme. Results this calculation are compared to those obtained from simpler Born approximation simplest perturbation theory approaches, some shortcomings latter pointed out. allows also for evaluating other related quantities such as power loss during...

Within a simple mean-field model (self-consistent Hartree approximation) we discuss the possibility of polaron formation on molecular wire as mechanism for negative differential resistance (NDR), switching, and/or hysteresis in I-V characteristic junctions. This differs from earlier proposed mechanisms charging and conformational change. The captures essential physics provides qualitative correspondence with experimental data. importance active redox centers molecule is indicated.

Within a phonon-assisted resonance level model we develop self-consistent procedure for calculating electron transport currents in molecular junctions with intermediate to strong electron-phonon interaction. The scheme takes into account the mutual influence of and phonon subsystems. It is based on second order cumulant expansion, used express correlation function shift generator terms momentum Green function. Equation motion (EOM) method obtain an approximate analog Dyson equation functions...

Heating and heat conduction in molecular junctions are considered within a general NEGF formalism. We obtain unified description of heating current carrying as well the electron phonon contributions to thermal flux, including their mutual influence. Ways calculate these contributions, relative importance ambiguities definitions discussed. A expression for flux is derived used new "measuring technique", define quantify 'local temperature' nonequilibrium systems. Superiority this measuring...

The interaction of light with molecular conduction junctions is attracting growing interest as a challenging experimental and theoretical problem on one hand, because its potential application characterization control tool the other. It stands at interface between two important fields, electronics plasmonics has attracted attention scientific potentially technological consequences. Here we review present state art this field, focusing several key phenomena applications: using switching...

We establish the foundations of a nonequilibrium theory quantum thermodynamics for noninteracting open systems strongly coupled to their reservoirs within framework Green functions (NEGF). The energy system and its coupling are controlled by slow external time-dependent force treated first order beyond quasistatic limit. derive four basic laws characterize reversible transformations. Stochastic is recovered in weak

We study heat transfers in a single level quantum dot strongly coupled to fermionic reservoirs and subjected time-dependent protocol modulating the energy as well dot-reservoir coupling strength. The dynamics is described using nonequilibrium Greens functions (NEGFs) evaluated first order beyond quasi-static driving. show that any definition expressed an change reservoir plus fraction of system-reservoir interaction not exact differential when along reversible isothermal transformations,...

The interaction of metal-molecule-metal junctions with light is considered within a simple generic model. We show, for the first time, that light-induced current in unbiased can take place when bridging molecule characterized by strong charge-transfer transition. same model shows current-induced emission under potential bias exceeds molecular excitation energy. Results based on realistic estimates molecule-lead coupling and molecule-radiation field suggest both effects should be observable.

A simple scheme, capable of treating transport in molecular junctions the language many-body states, is presented. By introducing an ansatz Liouville space, similar to generalized Kadanoff-Baym approximation, a quantum master equation (QME)-like expression derived starting from exact motion for Hubbard operators. Using effective space propagation, dressing standard diagrammatic one proposed. The scheme compared QME approach and its applicability calculations discussed.

We present a brief pedagogical review of theoretical Green's function methods applicable to open quantum systems out equilibrium, in general, and single molecule junctions, particular. briefly describe experimental advances molecular electronics then discuss different approaches. focus on methods. Two characteristic energy scales governing the physics are many-body interactions within junctions molecule–contact coupling. We, therefore, weak coupling as two limits that can be conveniently...

We address the line shape and widths observed in recent inelastic electron tunneling spectroscopy (IETS) experiments. The nonequilibrium Green function (NEGF) formalism is used to analyze effect of electron−phonon interaction on spectra. find that IETS shapes are sensitive junction parameters, particular position bridge electronic resonance molecule−lead coupling may be controlled experimentally. Intrinsic found dominated by molecular vibrations electron−hole pairs excitations lead(s) which...

The effect of electron-phonon coupling on the current noise in a molecular junction is investigated within simple model. model comprises one-level bridge representing level that connects between two free electron reservoirs and coupled to vibrational degree freedom mode. latter turn phonon bath represents thermal environment. We focus zero frequency spectrum study changes its behavior under weak strong interactions. In regime we find amplitude can increase or decrease as result opening an...

We consider several fundamental optical phenomena involving single molecules in biased metal-molecule-metal junctions. The molecule is represented by its highest occupied and lowest unoccupied molecular orbitals, the analysis involves simultaneous consideration of three coupled fluxes: electronic current through molecule, energy flow between electron-hole excitations leads, incident and/or emitted photon flux. Using a unified theoretical approach based on nonequilibrium Green’s function...

While heating of a current carrying Ohmic conductors is an obvious consequence the diffusive nature conduction in such systems, current-induced cooling has been recently reported some molecular junctions. In this paper, we demonstrate by simple models possibility junctions under applied bias, and discuss several mechanisms for effect. Our model characterized single electron tunneling between electrodes represented free reservoirs through system its levels, nuclear vibrations their...

Inelastic effects in the Coulomb blockade and Kondo regimes of electron transport through molecular junctions are considered within a simple nonequilibrium equation-of-motion (EOM) approach. The scheme is self-consistent can qualitatively reproduce main experimental observations vibrational features [H. Park et al., Nature (London) 407, 57 (2000)] [L. H. Yu Phys. Rev. Lett. 93, 266802 (2004)] regimes. Considerations similar to equilibrium EOM approach by Meir al. [Phys. 66, 3048 (1991); 70,...

We discuss several proposed explanations for the switching and negative differential resistance (NDR) behavior seen in some molecular junctions. Several theoretical models are discussed, we present results of electronic structure calculations on a series substituted oligo(phenylene ethynylene) molecules. It is shown that previously polaron model successful predicting NDR behavior, elaborated with image charge effects parameters from calculations. This now incorporates substituent includes...

We present a theory for Raman scattering by current-carrying molecular junctions. The approach combines nonequilibrium Green's function (NEGF) description of the junction with generalized formulation evaluating light signal. This generalizes our previous study [M. Galperin and A. Nitzan, Phys. Rev. Lett. 95, 206802 (2005); J. Chem. 124, 234709 (2006)] spectroscopy including vibrations developing machinery calculation state-to-state (Raman scattering) fluxes within NEGF formalism. For large...

We propose a self-consistent generalized quantum master equation (GQME) to describe electron transport through molecular junctions. In previous study [Esposito, M.; Galperin, M. Phys. Rev. B 2009, 79, 205303], we derived time-nonlocal GQME cure the lack of broadening effects in Redfield theory. To do so, free evolution used Born−Markov approximation close was replaced by standard evolution. present paper, backward leading time-local which allows for procedure generator. This approach is...

We consider the generation of pure spin currents by electric field driving. First, we discuss possibility pumping within a simple two-level bridge model. Then, apply scheme to study transport in single- and double-stranded DNA junctions. Within physically relevant range parameters show generating DNA, even absence spin–orbit coupling.

We present a method, based on characterizing efficiency fluctuations, to asses the performance of nanoscale thermoelectric junctions. This method accounts for effects typically arising in small junctions, namely, stochasticity junction's performance, quantum effects, and nonequilibrium features preventing linear response analysis. It is Green's function (NEGF) approach, which we use derive full counting statistics (FCS) heat work, turn allows us calculate statistical properties fluctuations....

Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention because their scientific importance potential applications. With the recent progress experimental techniques, especially by virtue scanning tunneling microscope (STM)-induced light emission, where current STM is used as an atomic-scale source for induction emission from molecule, it has become possible to investigate single-molecule at subnanometer spatial...

The influence of molecular vibration on the Seebeck coefficient is studied within a simple model. Results scattering theory approach are compared with those full self-consistent non-equilibrium Green's function scheme. We show, for reasonable choice parameters, that inelastic effects have non-negligible resulting junction. note may fail both quantitatively and qualitatively. results calculations parameters in good agreement recent measurements [Science 315, 1568 (2007)].