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31.
We investigate universal properties of strongly confined particles that turn out to be dramatically different from what is observed for electrons in atoms and molecules. For a large class of harmonically confined systems, such as small quantum dots and optically trapped atoms, many-body particle addition and removal energies, and energy gaps, are accurately obtained from single-particle eigenvalues. Transport blockade phenomena are related to the derivative discontinuity of the exchange-correlation functional. This implies that they occur very generally, with Coulomb blockade being a particular realization of a more general phenomenon. In particular, we predict a van der Waals blockade in cold atom gases in traps. 相似文献
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Ohne Zusammenfassung 相似文献
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S.M. Reimann M. Persson P.E. Lindelof M. Brack 《Zeitschrift für Physik B Condensed Matter》1997,101(3):377-385
The conductance of a circular quantum dot in a two-dimensional electron gas of a GaAlAs/GaAs heterostructure has been measured. Conductance oscillations as functions both of the magnetic field B and of the size of a dot confining about 1000 electrons are related to the formation of electronic shell structure. Modeling the dot by a circular billiard, we interpret the results semiclassically in terms of periodic orbit theory, providing a simple explanation of the B-periodic oscillations. A comparison to a harmonic confinement suitable for smaller quantum dots is given. 相似文献
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A detailed introduction to directed transport in Brownian motors occurring in spatially periodic systems far from equilibrium
is presented. We elucidate the prominent physical concepts and novel phenomena with a representative dissipative Brownian
motor dynamics. Its main ingredient is a thermal noise with time-dependent temperature modulations that drive the system out
of thermal equilibrium in a spatially asymmetric (ratchet-) potential. Yet, this asymmetric setup does not exhibit a concomitant
obvious bias into one or the other direction of motion. Symmetry conditions for the appearance (or not) of directed current,
its reversal upon variation of certain parameters, and various other generic features and applications are discussed. In addition,
we provide a systematic classification scheme for Brownian motor models and review historical landmark contributions to the
field.
Received: 9 November 2001 / Accepted: 14 January 2002 / Published online: 22 April 2002 相似文献
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Summary A novel synthesis to prepare dibenzo-8-quinolizinones8 is reported using the intramolecular cyclisation of the benzylated Reissert compounds6 for the key step. Methylation of8 by methyllithium gives partial deoxygenated coralynes10 which in turn can be reduced by NaBH4 yielding the 8-methyltetrahydro-protoberberines11. The structures are assigned by NMR-spectroscopy. 相似文献