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Condensed Matter Seminars
Condensed Matter
Thursday, January 20, 2005
4:00 PM
Physics Building, Room 204
Note special time.
Note special room.

Aditi Mitra
[Host: Paul Fendley]
Columbia University
"Nonequilibrium Transport Through a Phonon Coupled Molecule"

ABSTRACT:
The theory of nonequilibrium manybody systems is only partially understood, and developing the theory further is of relevance now as nanostructures (such as single molecule and NEMS devices) are routinely operated in the nonequilibrium regime. In this talk I will present a comprehensive theory for nonlinear transport through a single molecule device where the tunneling electrons are coupled to a vibrational mode of the molecule. I will present results for the current and the noise through
the device and show their sensitivity to phonon equilibration rates and hence to the steady state phonon distribution function. I will also outline a method to tackle the regime of low temperatures and strong electronphonon coupling where nonequilibrium conditions do not allow for
a variational treatment. Instead the key issue is the formulation of rate equations for the reduced density matrix that can be solved in the
semiclassical limit. The steadystate solutions lead to a multipeaked density matrix, implying an absence of bistability in the current but
structure in the noise. I will also demonstrate how departures from equilibrium produce decoherence that prevents the formation of
characteristically quantum features such as the polaron peak in the spectral function, and present generalizations of this method to other strongly correlated systems such as the nonequilibrium Kondo model.




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