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Condensed Matter Seminars
| Special Condensed Matter Seminar.
Monday, February 23, 2004
Physics Building, Room 204
Note special date.
Note special time.
Note special room.
[Host: Paul Fendley]
"Electron transport in granular arrays"
Electron-electron interactions in low-dimensional systems have
attracted a great deal of attention in recent years. We show that
arrays of large, strongly coupled quantum dots present an analytically
tractable, yet non-trivial model of such systems.
A single dot strongly coupled to leads exhibits almost no Coulomb
blockade (save for corrections that are exponentially small in the
dot-lead conductance). In the array geometry with large inter-grain
conductance g>>1, however, the interactions drive the system into
an insulating state with a charge gap proportional to exp(-g).
The latter reflects the energy cost to create a large-size,
unit-charge soliton -- the only charged excitation the system
supports. In 2d, such solitons bring about a
Berezinskii-Kosterlitz-Thouless crossover at a certain (g-dependent)
Upon changing the charge imbalance (e.g. by a gate voltage), the array
undergoes a phase transition into the pinned Wigner crystal state. The
model, thus, allows one to follow the system from a good metal (at
high temperature) all the way to the Wigner crystal insulator (at low
temperature) within a single framework.
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