Post-graduate theses
Current Record: 4861 of 6576
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Identifier |
000381548 |
Title |
Directed motion in Tight-Binding lattices |
Alternative Title |
Κατευθυνόμενη κίνηση σε πλέγματα ισχυρής δέσμευσης |
Author
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Τσατραφύλλης, Νικόλαος
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Thesis advisor
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Τσιρώνης, Γεώργιος
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Abstract |
Classical directed motion and quantum diffusion for a particle are studied in onedimension.
In the Classical regime, we examined through stochastic simulations in
the Langevin picture the motion of an over-damped Brownian particle in a periodic,
non-symmetric ratchet potential driven by time-correlated forces. We focused on two
extreme limits, the white noise limit where the correlation time goes to zero, where
we found numerically that white uncorrelated fluctuations cannot induce macroscopic
current. In the other extreme limit when the correlation time is very large, we noticed
that the time correlations of the noise can create a non zero current due to the
asymmetry of the potential, the well-known Ratchet effect. In the quantum regime we
studied the motion of a charged particle through the stochastic Liouville equation, using
analytical as well as numerical means, in three different one - dimensional discrete
tight-binding lattices : (i) the single-band, (ii) the two-band and (iii) the tree-band lattice,
in the presence/absence of a sinusoidal electric field. Additionally, the coupling of
the charged particle to the environment was taken into account in a phenomenological
way by adding proper terms in the Liouville equation. Quantum diffusion can been
seen in all cases except for the very special case of the linear lattice with an AC drive,
where dynamic localization appears for special values of the electric field’s parameters.
The phenomenon of dynamic localization, for the same parameter regime disappears
for the other types of lattices.
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Language |
English |
Subject |
Brownian motion |
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Diffusion |
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Discrete lattice |
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Liouville-von Neumann equation |
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Nonlinear system |
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Διακριτό Πλέγμα |
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Εξίσωση Liouville-von Neumann |
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Κίνηση Μπράουν |
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Μη-γραμμικό σύστημα |
Issue date |
2013-11-15 |
Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
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Type of Work--Post-graduate theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/e/9/1/metadata-dlib-1387348731-529216-22359.tkl
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Views |
598 |