Momentum Distribution Of Bosons Research Articles

Diboson Production at LHC and Tevatron

Measurements of the production of pairs of gauge bosons by the ATLAS and CMS experiments at the LHC and the CDF and D0 experiments at the Tevatron are summarized. Measured cross-sections are generally consistent with Standard Model predictions calculated at next-to-leading order in QCD. Transverse momentum distributions of bosons or leptons produced in these processs have been used to set limits on anomalous triple gauge boson couplings. Limits on WW and WWZ anomalous couplings are approaching, or exceeding, those derived from measurements at LEP, while those on neutral couplings are an order of magnitude more stringent than limits from LEP. First limits on anomalous quartic gauge boson couplings from the Tevatron and LHC are also presented.

Double peaks in the momentum distribution of cold polar molecules in the supersolid state

We study the checkerboard supersolid of hard-core bosonic polar molecules in a 2D square lattice. This supersolid shows a novel double-peak structure in the momentum distribution of bosons. The double peaks indicate coexistence of superfluidity and solidility. The corresponding peaks can be measured by the time-of-flight experiment and will become a clear evidence for the supersolid state. By exact quantum Monte Carlo calculations, we reveal temperature dependence of the momentum distribution in the supersolid phase. As a result, we observe successive developments of the two peaks.

Novel Mechanism of Supersolid of Ultracold Polar Molecules in Optical Lattices

We study the checkerboard supersolid of the hard-core Bose–Hubbard model with the dipole–dipole interaction. This supersolid is different from all other supersolids found in lattice models in the sense that superflow paths through which interstitials or vacancies can hop freely are absent in the crystal. By focusing on repulsive interactions between interstitials, we reveal that the long-range tail of the dipole–dipole interaction has the role of increasing the energy cost of domain wall formations. This effect produces the supersolid by the second-order hopping process of defects. We also perform exact quantum Monte Carlo simulations and observe a novel double peak structure in the momentum distribution of bosons, which is clear evidence of a supersolid. This can be measured by the time-of-flight experiment in optical lattice systems.

Two peaks in the momentum distribution of bosons in a weakly frustrated two-leg optical ladder

The ground-state properties of neutral hard-core bosons trapped in an optical two-leg ladder in the presence of an artificial magnetic field are studied. For a weak field, two separated peaks appear in the momentum distribution as a signature of the Meissner state in which bosons, carrying persistent currents on each leg, condense into finite-momentum states, while for a strong field, a central peak and tiny bumps associated with the vortex lattice structure indicate that the ground state is the vortex state.

Sharp peaks in the momentum distribution of bosons in optical lattices in the normal state

Cold atoms in optical lattices provide a unique laboratory for investigating quantum phase transitions between strongly correlated superfluid and Mott insulator phases1,2. One of the major bottlenecks in the analysis of experiments is a clear set of criteria for identifying the superfluid phase3. A ‘sharp’ interference pattern in time-of-flight experiments has been widely adopted as a signature of superfluidity4,5,6,7,8. Here, we show that sharp peaks are not a reliable diagnostic of superfluidity. Using large-scale quantum Monte Carlo simulations of the Bose–Hubbard model in three dimensions with up to N=1.4×104 particles, we calculate the momentum distribution n(k) as a function of temperature T and t/U, the ratio of hopping to the onsite repulsion. We find that even above the transition temperature Tc where both superfluid density and condensate fraction vanish, the interference pattern can nevertheless have sharp peaks riding over a broad background. We identify the true signature of the superfluid and give a deeper understanding of why such sharp peaks appear in the normal state.