24 research outputs found
Electronic friction in interacting systems
We consider effects of strong light-matter interaction on electronic friction
in molecular junctions within generic model of single molecule nano cavity
junction. Results of the Hubbard NEGF simulations are compared with mean-field
NEGF and generalized Head-Gordon and Tully approaches. Mean-field NEGF is shown
to fail qualitatively at strong intra-system interactions, while accuracy of
the generalized Head-Gordon and Tully results is restricted to situations of
well separated intra-molecular excitations, when bath induced coherences are
negligible. Numerical results show effects of bias and cavity mode pumping on
electronic friction. We demonstrate non-monotonic behavior of the friction on
the bias and intensity of the pumping field and indicate possibility of
engineering friction control in single molecule junctions.Comment: 19 pages, 4 figure
Current-induced forces for nonadiabatic molecular dynamics
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.Comment: 6 pages, 3 figure
Vibration-assisted upconversion of molecular luminescence induced by scanning tunneling microscopy
Control and enhancement of single-molecule electroluminescence through strong light-matter coupling
The energetic positions of molecular electronic states at molecule/electrode
interfaces are crucial factors for determining the transport and optoelectronic
properties of molecular junctions. Strong light--matter coupling offers a
potential for manipulating these factors, enabling to boost in the efficiency
and versatility of these junctions. Here, we investigate electroluminescence
from single-molecule junctions in which the molecule is strongly coupled with
the vacuum electromagnetic field in a plasmonic nanocavity. We demonstrate an
improvement in the electroluminescence efficiency by employing the strong
light--matter coupling in conjunction with the characteristic feature of
single-molecule junctions to selectively control the formation of the
lowest-energy excited state. The mechanism of efficiency improvement is
discussed based on the energetic position and composition of the formed
polaritonic states. Our findings indicate the possibility to manipulate
optoelectronic conversion in molecular junctions by strong light--matter
coupling and contribute to providing design principles for developing efficient
molecular optoelectronic devices
Towards Noise Simulation in Interacting Nonequilibrium Systems Strongly Coupled to Baths
Progress in experimental techniques at nanoscale made measurements of noise
in molecular junctions possible. These data are important source of information
not accessible through average flux measurements. Emergence of optoelectronics,
recently shown possibility of strong light-matter couplings, and developments
in the field of quantum thermodynamics are making counting statistics
measurements of even higher importance. Theoretical methods for noise
evaluation in first principles simulations can be roughly divided into
approaches applicable in the case of weak intra-system interactions, and those
treating strong interactions for systems weakly coupled to baths. We argue that
due to structure of its diagrammatic expansion and the fact of utilizing
many-body states as a basis of its formulation recently introduced
nonequilibrium Hubbard Green functions formulation is a relatively inexpensive
method suitable for evaluation of noise characteristics in first principles
simulations over wide range of parameters. We illustrate viability of the
approach by simulations of noise and noise spectrum within generic models for
non-, weakly and strongly interacting systems. Results of the simulations are
compared to exact data (where available) and to simulations performed within
approaches best suited for each of the three parameter regimes.Comment: 19 pages, 5 figure