A5035641566- Molecular Junctions and Nanostructures
- Spectroscopy and Quantum Chemical Studies
- Advanced Thermodynamics and Statistical Mechanics
- Quantum and electron transport phenomena
- Photochemistry and Electron Transfer Studies
- Advanced Chemical Physics Studies
- Strong Light-Matter Interactions
- Electrochemical Analysis and Applications
- Material Dynamics and Properties
- Mechanical and Optical Resonators
- Force Microscopy Techniques and Applications
- stochastic dynamics and bifurcation
- Thermal Radiation and Cooling Technologies
- Gold and Silver Nanoparticles Synthesis and Applications
- Plasmonic and Surface Plasmon Research
- Quantum, superfluid, helium dynamics
- Quantum Information and Cryptography
- Thermal properties of materials
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum optics and atomic interactions
- Surface and Thin Film Phenomena
- Theoretical and Computational Physics
- Nonlinear Dynamics and Pattern Formation
- Ionic liquids properties and applications
- Organic Electronics and Photovoltaics
University of Pennsylvania
2016-2025
California University of Pennsylvania
2022-2025
Tel Aviv University
2015-2024
Arizona State University
2019
Freie Universität Berlin
2006-2016
University of California, San Diego
2009-2013
City University of New York
2013
City College of New York
1984-2013
Northwestern University
1988-2009
Holon Institute of Technology
2007-2009
Molecular conductance junctions are structures in which single molecules or small groups of conduct electrical current between two electrodes. In such junctions, the connection molecule and electrodes greatly affects current-voltage characteristics. Despite several experimental theoretical advances, including understanding simple systems, there is still limited correspondence studies these systems.
A theory for surface enhanced Raman scattering (SERS) is developed. Effects due to realistic geometry and dielectric properties are included. Three sources of noted: the image dipole enhancement effect, increase local field (’’lightning rod’’ effect), resonant excitation plasmons. The modeled as a hemispheroid protruding from conducting plane, although other models considered. spherical limit discussed in some detail molecular orientation effects Cross sections Mie, Rayleigh, derived.
Electron transmission through molecules and molecular interfaces has been a subject of intensive research due to recent interest in electron-transfer phenomena underlying the operation scanning-tunneling microscope on one hand, properties bridges between conducting leads other. In these processes, traditional view electron transfer donor acceptor species gives rise novel molecule as current-carrying conductor, observables such rates yields are replaced by conductivities, or more generally...
Stable molecular switches Many single-molecule current have been reported, but most show poor stability because of weak contacts to metal electrodes. Jia et al. covalently bonded a diarylethene molecule graphene electrodes and achieved stable photoswitching at room temperature (see the Perspective by Frisbie). The incorporation short bridging alkyl chains between decoupled their pielectron systems allowed fast conversion open closed ring states. Science , this issue p. 1443 ; see also 1394
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...
Optical properties of small dielectric spheroids with or without adsorbed molecules are studied theoretically. Expressions for the absorption line shapes, radiative and nonradiative decay rates, quantum yields derived. In case a molecule near spheroid magnitudes differ dramatically from corresponding plane.
The enhancements of normal Raman scattering, resonance and fluorescence from molecules adsorbed on identical, well-characterized, silver-island films are reported. enhancement arises the electromagnetic interaction between electronic plasma silver islands. A hierarchy ratios is found, with typical values 105 for RS, 103 RRS 10−1 to 10 fluorescence, depending quantum yield molecular fluorescence. model, developed heuristic grounds substantiated using density matrix formalism, describes light...
Rectification of heat transfer in nanodevices can be realized by combining the system inherent anharmonicity with structural asymmetry. we analyze this phenomenon within simplest anharmonic -a spin-boson nanojunction model. We consider two variants model that yield, for first time, analytical solutions: a linear separable which reservoirs contribute additively, and non-separable suitable stronger system-bath interaction. Both models show asymmetric (rectifying) conduction when couplings to...
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...
Recent experiments suggest that vibrational strong coupling (VSC) may significantly modify ground-state chemical reactions and their rates even without external pumping. The intrinsic mechanism of this “vacuum-field catalysis” remains largely unclear. Generally, modifications thermal in the ground electronic states can be caused by equilibrium or non-equilibrium effects. former are associated with reactant distribution as expressed transition state theory reaction rates, while latter stem...
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.
The effect of dephasing and relaxation on electron transfer in bridged molecular systems is investigated using a simple model. interaction between the system thermal environment described level Redfield theory, modified when needed for description steady-state situations. Noting that transient as well measurements are possible such system, we discuss relationship rates obtained from these different types experiments and, particular, conditions under which same. Also, formal relation rate...
A dynamic bond percolation model is defined and studied. The intended to describe diffusion of small particles (ions, electrons) in a medium which statistically disordered (as ordinary percolation), but also undergoing rearrangement processes on timescale short compared the observation time. should be applicable polymeric solid electrolytes, where orientational motions polymer (which are responsible for configurational entropy) cause motion (polymer) (alkali ions) diffuse. characterized by...
We consider phononic heat transport through molecular chains connecting two thermal reservoirs. For relatively short molecules at normal temperatures we find, using classical stochastic simulations, that conduction is dominated by the harmonic part of force-field. develop a general theory for in three-dimensions. Our approach uses standard formalism leads to generalized (quantum) Langevin equation system coupled bath, however driving and relaxation terms are considered separately way...
A simplified theory of enhanced ultraviolet, visible, and infrared photochemistry near rough dielectric metallic surfaces is described numerically investigated. Protrusions on a surface are modeled as isolated microscopic spheres. We formulate classical equations motion for molecules interacting with electromagnetic fields such material The model incorporates (a) dipole–dipole coupling between absorbing the large, induced dipoles created in spheres irradiated Mie resonances, (b) dissipative...
In this paper we advance a model Hamiltonian for direct vibrational relaxation of guest molecule in host lattice. General expressions the rate constant are derived utilizing generating function method, elucidating gross features class multiphonon phenomena. Explicit theoretical results were obtained two temperature regions: moderately low temperatures below characteristic Debye and high limit. range exhibits nearly exponential variation with order processes, revealing energy gap law, an...
Protonic diffusion in hydrogen-bonded networks, ionic conduction polymeric solid electrolytes, and other processes which the carrier transport mechanism involves motion of host medium on a time scale comparable to that itself require generalization usual models based hopping static medium. Under assumption this concurrent can be modeled by random reassignment (or ``renewal'') probabilities, with constant probability \ensuremath{\lambda} per unit for renewal occur, effects frequency-dependent...