1,016 research outputs found
Exotic Superconducting Phases of Ultracold Atom Mixtures on Triangular Lattices
We study the phase diagram of two-dimensional Bose-Fermi mixtures of
ultracold atoms on a triangular optical lattice, in the limit when the velocity
of bosonic condensate fluctuations is much larger than the Fermi velocity.
We contrast this work with our previous results for a square lattice system
in Phys. Rev. Lett. {\bf 97}, 030601 (2006).
Using functional renormalization group techniques we show that the phase
diagrams for a triangular lattice contain exotic superconducting phases. For
spin-1/2 fermions on an isotropic lattice we find a competition of -, -,
extended -, and -wave symmetry, as well as antiferromagnetic order. For
an anisotropic lattice, we further find an extended p-wave phase. A Bose-Fermi
mixture with spinless fermions on an isotropic lattice shows a competition
between - and -wave symmetry.
These phases can be traced back to the geometric shapes of the Fermi surfaces
in various regimes, as well as the intrinsic frustration of a triangular
lattice.Comment: 6 pages, 4 figures, extended version, slight modification
In situ measurement of the dynamic structure factor in ultracold quantum gases
We propose an experimental setup to efficiently measure the dynamic structure
factor of ultracold quantum gases. Our method uses the interaction of the
trapped atomic system with two different cavity modes, which are driven by
external laser fields. By measuring the output fields of the cavity the dynamic
structure factor of the atomic system can be determined. Contrary to previous
approaches the atomic system is not destroyed during the measurement process.Comment: 5 pages, 3 figure
Luminescence quenching of the triplet excimer state by air traces in gaseous argon
While developing a liquid argon detector for dark matter searches we
investigate the influence of air contamination on the VUV scintillation yield
in gaseous argon at atmospheric pressure. We determine with a radioactive
alpha-source the photon yield for various partial air pressures and different
reflectors and wavelength shifters. We find for the fast scintillation
component a time constant tau1= 11.3 +- 2.8 ns, independent of gas purity.
However, the decay time of the slow component depends on gas purity and is a
good indicator for the total VUV light yield. This dependence is attributed to
impurities destroying the long-lived argon excimer states. The population ratio
between the slowly and the fast decaying excimer states is determined for
alpha-particles to be 5.5 +-0.6 in argon gas at 1100 mbar and room temperature.
The measured mean life of the slow component is tau2 = 3.140 +- 0.067 microsec
at a partial air pressure of 2 x 10-6 mbar.Comment: 7 pages submitted to NIM
Neer vs. anatomically based humeral prostheses - Biomechanical comparison with a comprehensive model of the shoulder
Quantum fluctuations in thin superconducting wires of finite length
In one dimensional wires, fluctuations destroy superconducting long-range
order and stiffness at finite temperatures; in an infinite wire, quasi-long
range order and stiffness survive at zero temperature if the wire's
dimensionless admittance is large, . We analyze the
disappearance of this superconductor-insulator quantum phase transition in a
finite wire and its resurrection due to the wire's coupling to its environment
characterized through the dimensionless conductance . Integrating over phase
slips, we determine the flow of couplings and establish the -- phase
diagram.Comment: 4 pages, 2 figure
Commensurate-incommensurate transition of cold atoms in an optical lattice
An atomic gas subject to a commensurate periodic potential generated by an
optical lattice undergoes a superfluid--Mott insulator transition. Confining a
strongly interacting gas to one dimension generates an instability where an
arbitrary weak potential is sufficient to pin the atoms into the Mott state;
here, we derive the corresponding phase diagram. The commensurate pinned state
may be detected via its finite excitation gap and the Bragg peaks in the static
structure factor.Comment: 4 pages, 2 figure
Repulsively bound atom pairs: Overview, Simulations and Links
We review the basic physics of repulsively bound atom pairs in an optical
lattice, which were recently observed in the laboratory, including the theory
and the experimental implementation. We also briefly discuss related many-body
numerical simulations, in which time-dependent Density Matrix Renormalisation
Group (DMRG) methods are used to model the many-body physics of a collection of
interacting pairs, and give a comparison of the single-particle quasimomentum
distribution measured in the experiment and results from these simulations. We
then give a short discussion of how these repulsively bound pairs relate to
bound states in some other physical systems.Comment: 7 pages, 3 figures, Proceedings of ICAP-2006 (Innsbruck
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