6,782 research outputs found
Exotic phases of interacting p-band bosons
We study a model of interacting bosons that occupy the first excited p-band
states of a two-dimensional optical lattice. In contrast to the much studied
single band Bose-Hubbard Hamiltonian, this more complex model allows for
non-trivial superfluid phases associated with condensation at non-zero momentum
and staggered order of the orbital angular momentum in addition to the
superfluid-Mott insulator transition. More specifically, we observe staggered
orbital angular momentum order in the Mott phase at commensurate filling and
superfluidity at all densities. We also observe a transition between the
staggered angular momentum superfluid phase and a striped superfluid, with an
alternation of the phase of the superfluid along one direction. The transition
between these two phases was observed in a recent experiment, which is then
qualitatively well described by our model.Comment: 8 pages, 12 figure
P-band in a rotating optical lattice
We investigate the effects of rotation on the excited bands of a tight
binding lattice, focusing particulary on the first excited (p-) band. Both the
on-site energies and the hopping between lattice sites are modified by the
effective magnetic field created by rotation, causing a non-trivial splitting
and magnetic fine structure of the p-band. We show that Peierls substitution
can be modified to describe p-band under rotation, and use this method to
derive an effective Hamiltonian. We compare the spectrum of the effective
Hamiltonian with a first principles calculation of the magnetic band structure
and find excellent agreement, confirming the validity of our approach. We also
discuss the on-site interaction terms for bosons and argue that many-particle
phenomena in a rotating p-band can be investigated starting from this effective
Hamiltonian.Comment: 7 pages, 4 figures, new discussion of effective Hamiltonian,
references adde
Loading of bosons in optical lattices into the p band
We present a method for transferring bosonic atoms residing on the lowest
s-band of an optical lattice to the first excited p-bands. Our idea hinges on
resonant tunneling between adjacent sites of accelerated lattices. The
acceleration effectively shifts the quasi-bound energies on each site such that
the system can be cast into a Wannier-Stark ladder problem. By adjusting the
acceleration constant, a situation of resonant tunneling between the s- and
p-bands is achievable. Within a mean-field model, considering 87Rb atoms, we
demonstrate population transfer from the s- to the p-bands with around 95 %
efficiency. Nonlinear effects deriving from atom-atom interactions, as well as
coupling of the quasi bound Wannier-Stark states to the continuum, are
considered.Comment: 8 pages, 7 figure
Dynamical instability and loss of p-band bosons in optical lattices
We study how the bosonic atoms on the excited p-band of an optical lattice
are coupled to the lowest s-band and the 2nd excited d-band. We find that in
some parameter regimes the atom-atom interactions can cause a dynamical
instability of the p-band atoms towards decay to the s- and d-bands.
Furthermore, even when dynamical instability is not expected s- and d-bands can
become substantially populated.Comment: 7 figures, minor changes to the earlier versio
Quantifying Temporal Decorrelation over Boreal Forest at L- and P-band
Temporal decorrelation is probably the most critical factor towards a successful implementation of Pol-InSAR parameter inversion techniques in terms of repeat-pass InSAR scenarios. In this paper the effect and impact of temporal decorrelation at L- and P-band is quantified. For this, data acquired by DLR’s E-SAR system in the frame of the BioSAR campaign (initiated and sponsored by the European Space Agency (ESA)) over boreal forest with variable temporal baseline in 2007 in Sweden are analyzed. For validation lidar data and ground measurements data are used
Quantum Antiferromagnetism of Fermions in Optical Lattices with Half-filled p-band
We study Fermi gases in a three-dimensional optical lattice with five
fermions per site, i.e. the s-band is completely filled and the p-band with
three-fold degeneracy is half filled. We show that, for repulsive interaction
between fermions, the system will exhibit spin-3/2 antiferromagnetic order at
low temperature. This conclusion is obtained in strong interaction regime by
strong coupling expansion which yields an isotropic spin-3/2 Heisenberg model,
and also in weak interaction regime by Hatree-Fock mean-field theory and
analysis of Fermi surface nesting. We show that the critical temperature for
this antiferromagnetism of a p-band Mott insulator is about two orders of
magnitudes higher than that of an -band Mott insulator, which is close to
the lowest temperature attainable nowadays
Effective action approach to the p-band Mott insulator and superfluid transition
Motivated by the recent experiment on p-orbital band bosons in optical
lattices, we study theoretically the quantum phases of Mott insulator and
superfluidity in two-dimensions. The system features a novel superfluid phase
with transversely staggered orbital current at weak interaction, and a Mott
insulator phase with antiferro-orbital order at strong coupling and
commensurate filling. We go beyond mean field theory and derive from a
microscopic model an effective action that is capable of describing both the
p-band Mott insulating and superfluid phases in strong coupling. We further
calculate the excitation spectra near the quantum critical point and find two
gapless modes away from the tip of the Mott lobe but four gapless modes at the
tip. Our effective theory reveals how the phase coherence peak builds up in the
Mott regime when approaching the critical point. We also discuss the finite
temperature phase transition of p-band superfluidity.Comment: 9+epsilon pages, 7 figures, one appendix added, accepted by Phys.
Rev.
Magnetism of Cold Fermionic Atoms on p-Band of an Optical Lattice
We carry out \textit{ab initio} study of ground state phase diagram of
spin-1/2 cold fermionic atoms within two-fold degenerate -band of an
anisotropic optical lattice. Using the Gutzwiller variational approach, we show
that a robust ferromagnetic phase exists for a vast range of band fillings and
interacting strengths. The ground state crosses over from spin density wave
state to spin-1 Neel state at half filling. Additional harmonic trap will
induce spatial separation of varies phases. We also discuss several relevant
observable consequences and detection methods. Experimental test of the results
reported here may shed some light on the long-standing issue of itinerant
ferromagnetism.Comment: 5 pages, 4 figure
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