**Colloquium**

Friday, March 21, 2003

4:00 PM

Physics Building, Room 204

Note special time.

Note special room.

## "Interactions and Disorder in Quantum Dots: A New Large-g Approach"

**Ganpathy Murthy , University of Kentucky**

[Host: Eugene Kolomeisky]

ABSTRACT:

Understanding the combined effects of disorder and interactions in
electronic systems has emerged as one of the most challenging
theoretical problems in condensed matter physics. It turns out that
one can solve this problem non-perturbatively in both disorder and
interactions in the regime when the system is finite (as in a quantum
dot) but its dimensionless conductance g under open-lead conditions
is large. This regime is experimentally interesting for the statistics
of Coulomb Blockade in quantum dots and persistent currents in rings
threaded by a flux. First some RG work will be described which shows
that a disordered quantum dot with Fermi liquid interactions can be in
one of two phases; one controlled by the so-called Universal
Hamiltonian and another regime where interactions become large. These
two are separated in the infinite-g limit by a second-order phase
transition. I will show how to solve for the strong-coupling phase, which is
characterized by a Fermi surface distortion, by a large-N
approximation (where N=g is in fact large for realistic
systems). Predictions will be presented for finite but large g for
the statistics of the Coulomb Blockade peak spacings and other
correlators. Finally, the relationship of these results to
puzzles in persistent currents in mesoscopic rings will be
presented.

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