3,236 research outputs found
New Numerical Results Indicate a Half-Filling SU(4) Kondo State in Carbon Nanotubes
Numerical calculations simulate transport experiments in carbon nanotube
quantum dots (P. Jarillo-Herrero et al., Nature 434, 484 (2005)), where a
strongly enhanced Kondo temperature T_K ~ 8K was associated with the SU(4)
symmetry of the Hamiltonian at quarter-filling for an orbitally
double-degenerate single-occupied electronic shell. Our results clearly suggest
that the Kondo conductance measured for an adjacent shell with T_K ~ 16K,
interpreted as a singlet-triplet Kondo effect, can be associated instead to an
SU(4) Kondo effect at half-filling. Besides presenting spin-charge Kondo
screening similar to the quarter-filling SU(4), the half-filling SU(4) has been
recently associated to very rich physical behavior, including a
non-Fermi-liquid state (M. R. Galpin et al., Phys. Rev. Lett. 94, 186406
(2005)).Comment: 7 pages, 7 figure
Structural investigations on -FeGe at high pressure and low temperature
The structural parameters of -FeGe have been determined at ambient
conditions using single crystal refinement. Powder diffraction have been
carried out to determine structural properties and compressibility for
pressures up to 30 GPa and temperatures as low as 82 K. The discontinuous
change in the pressure dependence of the shortest Fe-Ge interatomic distance
might be interpreted as a symmetry-conserving transition and seems to be
related to a magnetic phase boundary line.Comment: 4 pages, 5 figure
Strong coupling of a qubit to shot noise
We perform a nonperturbative analysis of a charge qubit in a double quantum
dot structure coupled to its detector. We show that strong detector-dot
interaction tends to slow down and halt coherent oscillations. The transitions
to a classical and a low-temperature quantum overdamping (Zeno) regime are
studied. In the latter, the physics of the dissipative phase transition
competes with the effective shot noise.Comment: 5 pages, 4 figure
Electron transport through Aharonov-Bohm interferometer with laterally coupled double quantum dots
We theoretically investigate electron transport through an Aharonov-Bohm
interferometer containing laterally coupled double quantum dots. We introduce
the indirect coupling parameter , which characterizes the strength of
the coupling via the reservoirs between two quantum dots.
indicates the strongest coupling, where only a single mode contributes to the
transport in the system. Two conduction modes exist in a system where
. The interference effects such as the Fano resonance and the
Aharonov-Bohm oscillation are suppressed as the absolute value of the parameter
decreases from 1. The linear conductance does not depend on the flux
when since it corresponds to independent coupling of the dots to the
reservoir modes.Comment: 15 pages, 13 figure
A Pessimistic Approach to Trust in Mobile Agent Platforms
To be provided later
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