924 research outputs found
Magnetism and domain formation in SU(3)-symmetric multi-species Fermi mixtures
We study the phase diagram of an SU(3)-symmetric mixture of three-component
ultracold fermions with attractive interactions in an optical lattice,
including the additional effect on the mixture of an effective three-body
constraint induced by three-body losses. We address the properties of the
system in by using dynamical mean-field theory and variational Monte
Carlo techniques. The phase diagram of the model shows a strong interplay
between magnetism and superfluidity. In the absence of the three-body
constraint (no losses), the system undergoes a phase transition from a color
superfluid phase to a trionic phase, which shows additional particle density
modulations at half-filling. Away from the particle-hole symmetric point the
color superfluid phase is always spontaneously magnetized, leading to the
formation of different color superfluid domains in systems where the total
number of particles of each species is conserved. This can be seen as the SU(3)
symmetric realization of a more general tendency to phase-separation in
three-component Fermi mixtures. The three-body constraint strongly disfavors
the trionic phase, stabilizing a (fully magnetized) color superfluid also at
strong coupling. With increasing temperature we observe a transition to a
non-magnetized SU(3) Fermi liquid phase.Comment: 36 pages, 17 figures; Corrected typo
Critical Level Statistics in Two-dimensional Disordered Electron Systems
The level statistics in the two dimensional disordered electron systems in
magnetic fields (unitary ensemble) or in the presence of strong spin-orbit
scattering (symplectic ensemble) are investigated at the Anderson transition
points. The level spacing distribution functions 's are found to be
independent of the system size or of the type of the potential distribution,
suggesting the universality. They behave as in the small region in
the former case, while rise is seen in the latter.Comment: LaTeX, to be published in J. Phys. Soc. Jpn. (Letter) Nov., Figures
will be sent on reques
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Simultaneous enhancement in open circuit voltage and short circuit current of hybrid organic-inorganic photovoltaics by inorganic interfacial modification
Here, we investigate the model poly(3-hexathiophene)/ZnO system and show that by introducing a caesium carbonate interlayer, a simultaneous increase in all photovoltaic parameters can be achieved.We kindly acknowledge Prof. Uwe Bunz and Prof. Annemarie Pucci for access to device fabrication facilities and AFM measurements, respectively. P.E.H. thanks the Excellence Initiative for Funding. A.A.B. is a Royal Society University Research Fellow.This is the author accepted manuscript. The final version is available from The Royal Society of Chemistry via http://dx.doi.org/10.1039/C5TC03206
Interference in interacting quantum dots with spin
We study spectral and transport properties of interacting quantum dots with
spin. Two particular model systems are investigated: Lateral multilevel and two
parallel quantum dots. In both cases different paths through the system can
give rise to interference. We demonstrate that this strengthens the multilevel
Kondo effect for which a simple two-stage mechanism is proposed. In parallel
dots we show under which conditions the peak of an interference-induced orbital
Kondo effect can be split.Comment: 8 pages, 8 figure
Relation between Energy Level Statistics and Phase Transition and its Application to the Anderson Model
A general method to describe a second-order phase transition is discussed. It
starts from the energy level statistics and uses of finite-size scaling. It is
applied to the metal-insulator transition (MIT) in the Anderson model of
localization, evaluating the cumulative level-spacing distribution as well as
the Dyson-Metha statistics. The critical disorder and the critical
exponent are computed.Comment: 9 pages, Latex, 6 PostScript figures in uuencoded compressed tar file
are appende
Singlet-Triplet Transition in lateral Quantum Dots: A Numerical Renormalization Group Study
We discuss transport through a lateral quantum dot in the vicinity of a
singlet-triplet spin transition in its ground state. Extracting the scattering
phase shifts from the numerical renormalization group spectra, we determine the
linear conductance at zero temperature as a function of a Zeeman field and the
splitting of the singlet and triplet states. We find reduced low-energy
transport, and a non-monotonic magnetic field dependence both in the singlet
and the triplet regime. For a generic set of dot parameters and no Zeeman
splitting, the singlet-triplet transition may be identified with the
conductance maximum. The conductance is least sensitive to the magnetic field
in the region of the transition, where it decreases upon application of a
magnetic field. Our results are in good agreement with recent experimental
data.Comment: 9 pages Revtex, 10 eps figure
Spectral Properties of Three Dimensional Layered Quantum Hall Systems
We investigate the spectral statistics of a network model for a three
dimensional layered quantum Hall system numerically. The scaling of the
quantity is used to determine the critical exponent for
several interlayer coupling strengths. Furthermore, we determine the level
spacing distribution as well as the spectral compressibility at
criticality. We show that the tail of decays as with
and also numerically verify the equation
, where is the correlation dimension and the
spatial dimension.Comment: 4 pages, 5 figures submitted to J. Phys. Soc. Jp
Kondo Correlations and the Fano Effect in Closed AB-Interferometers
We study the Fano-Kondo effect in a closed Aharonov-Bohm (AB) interferometer
which contains a single-level quantum dot and predict a frequency doubling of
the AB oscillations as a signature of Kondo-correlated states. Using Keldysh
formalism, Friedel sum rule and Numerical Renormalization Group, we calculate
the exact zero-temperature linear conductance as a function of AB phase
and level position . In the unitary limit, reaches
its maximum at . We find a Fano-suppressed Kondo plateau
for similar to recent experiments.Comment: 4 pages, 4 eps figure
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