2,076 research outputs found
Transmission phase of a quantum dot: Testing the role of population switching
We propose a controlled experiment to clarify the physical mechanism causing
phase lapses of the amplitude for electron transmission through nanoscale
devices. Such lapses are generically observed in valleys between adjacent
Coulomb--blockade peaks. The experiment involves two quantum dots embedded in
the same arm of an Aharonov--Bohm interferometer. It offers a decisive test of
"population switching", one of the leading contenders for an explanation of the
phenomenon.Comment: 4 pages, 4 figure
Yang-Lee Edge Singularity on a Class of Treelike Lattices
The density of zeros of the partition function of the Ising model on a class
of treelike lattices is studied. An exact closed-form expression for the
pertinent critical exponents is derived by using a couple of recursion
relations which have a singular behavior near the Yang-Lee edge.Comment: 9 pages AmsTex, 2 eps figures, to appear in J.Phys.
Nonmonotonic charge occupation in double dots
We study the occupation of two electrostatically-coupled single-level quantum
dots with spinless electrons as a function of gate voltage. While the total
occupation of the double-dot system varies monotonically with gate voltage, we
predict that the competition between tunneling and Coulomb interaction can give
rise to a nonmonotonic filling of the individual quantum dots. This
non-monotonicity is a signature of the correlated nature of the many-body
wavefunction in the reduced Hilbert space of the dots. We identify two
mechanisms for this nonmonotonic behavior, which are associated with changes in
the spectral weights and the positions, respectively, of the excitation spectra
of the individual quantum dots. An experimental setup to test these predictions
is proposed.Comment: 4 pages, 5 figure
Correlations of conductance peaks and transmission phases in deformed quantum dots
We investigate the Coulomb blockade resonances and the phase of the
transmission amplitude of a deformed ballistic quantum dot weakly coupled to
leads. We show that preferred single--particle levels exist which stay close to
the Fermi energy for a wide range of values of the gate voltage. These states
give rise to sequences of Coulomb blockade resonances with correlated peak
heights and transmission phases. The correlation of the peak heights becomes
stronger with increasing temperature. The phase of the transmission amplitude
shows lapses by between the resonances. Implications for recent
experiments on ballistic quantum dots are discussed.Comment: 29 pages, 9 eps-figure
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