Search results for "GASES"
showing 10 items of 1098 documents
Formation of spatial shell structures in the superfluid to Mott insulator transition
2006
International audience; We report on the direct observation of the transition from a compressible superfluid to an incompressible Mott insulator by recording the in-trap density distribution of a Bosonic quantum gas in an optical lattice. Using spatially selective microwave transitions and spin changing collisions, we are able to locally modify the spin state of the trapped quantum gas and record the spatial distribution of lattice sites with different filling factors. As the system evolves from a superfluid to a Mott insulator, we observe the formation of a distinct shell structure, in good agreement with theory.
Minimum instances of topological matter in an optical plaquette
2007
We propose experimental schemes to create and probe minimum forms of different topologically ordered states in a plaquette of an optical lattice: Resonating Valence Bond, Laughlin and string-net condensed states. We show how to create anyonic excitations on top of these liquids and detect their fractional statistics. In addition, we propose a way to design a plaquette ring-exchange interaction, the building block Hamiltonian of a lattice topological theory. Our preparation and detection schemes combine different techniques already demonstrated in experiments with atoms in optical superlattices.
Coherent collisional spin dynamics in optical lattices
2005
We report on the observation of coherent, purely collisionally driven spin dynamics of neutral atoms in an optical lattice. For high lattice depths, atom pairs confined to the same lattice site show weakly damped Rabi-type oscillations between two-particle Zeeman states of equal magnetization, induced by spin changing collisions. This paves the way towards the efficient creation of robust entangled atom pairs in an optical lattice. Moreover, measurement of the oscillation frequency allows for precise determination of the spin-changing collisional coupling strengths, which are directly related to fundamental scattering lengths describing interatomic collisions at ultracold temperatures.
State preparation and dynamics of ultracold atoms in higher lattice orbitals
2007
We report on the realization of a multi-orbital system with ultracold atoms in the excited bands of a 3D optical lattice by selectively controlling the band population along a given lattice direction. The lifetime of the atoms in the excited band is found to be considerably longer (10-100 times) than the characteristic time scale for inter-site tunneling, thus opening the path for orbital selective many-body physics with ultracold atoms. Upon exciting the atoms from an initial lowest band Mott insulating state to higher lying bands, we observe the dynamical emergence of coherence in 1D (and 2D), compatible with Bose-Einstein condensation to a non-zero momentum state.
Effective Charge of the Higgs Boson
1997
The Higgs-boson lineshape is studied within the pinch technique resummation formalism. It is shown that any resonant Higgs-boson amplitude contains a universal part which is gauge independent, renormalization-group invariant, satisfies the optical and equivalence theorems, and constitutes the natural extension of the QED effective charge to the case of the Higgs scalar.
Measurements of Multi-boson production, Trilinear and Quartic Gauge Couplings with the ATLAS detector
2016
The ATLAS collaboration has carried a set of measurements that provide stringent tests of the electroweak sector of Standard Model, specifically on di- and multi-boson production cross sections and on triple and quartic gauge-boson couplings. Such measurements include cross sections for WV (V=W or Z) production in the leptonic or semileptonic channels, the production of a W or Z boson in association with photons, a Z boson in the vector-boson fusion channel and two same-charge W bosons in the vector-boson scattering channel. These measurements are compared to (N)NLO predictions of the Standard Model and provide model-independent constraints on new physics, by setting limits on anomalous gau…
Co-existence and shell structures of several superfluids in trapped three-component Fermi mixtures
2006
We study the properties of a trapped interacting three component Fermi gas. We assume that one of the components can have a different mass from the other two. We calculate the different phases of the three component mixture and find a rich variety of different phases corresponding to different pairing channels, and simple ways of tuning the system from one phase to another. In particular, we predict co-existence of several different superfluids in the trap, forming a shell structure, and phase transitions from this mixture of superfluids to a single superfluid when the system parameters or temperature is varied. Such shell structures realize superfluids with a non-trivial spatial topology a…
Condensation of classical nonlinear waves
2005
We study the formation of a large-scale coherent structure (a condensate) in classical wave equations by considering the defocusing nonlinear Schr\"odinger equation as a representative model. We formulate a thermodynamic description of the condensation process by using a wave turbulence theory with ultraviolet cut-off. In 3 dimensions the equilibrium state undergoes a phase transition for sufficiently low energy density, while no transition occurs in 2 dimensions, in analogy with standard Bose-Einstein condensation in quantum systems. Numerical simulations show that the thermodynamic limit is reached for systems with $16^3$ computational modes and greater. On the basis of a modified wave tu…
Exciton, biexciton and trion recombination dynamics in a single quantum dot under selective optical pumping
2008
Continuous wave- and time-resolved micro-photoluminescence spectroscopy has been performed on single InAs self-assembled quantum dots grown on GaAs. The presence of residual impurities (donors and acceptors) in samples with low dot density opens the possibility to switch from trion to neutral exciton states inside quantum dots by selective optical pumping. We propose a microstate model to describe the recombination dynamics of all the excitonic especies (neutral exciton, positive/negative trion and biexciton) under the considered optical pumping conditions when increasing the excitation power. © 2007 Elsevier B.V. All rights reserved.
On Gauge Invariance of Breit-Wigner Propagators
1993
We present an approach to bosonic ($Z^0, W^{\pm}$) as well as fermionic (top-quark) Breit-Wigner propagators which is consistent with gauge invariance arguments. In particular, for the $Z^0$-boson propagator we extend previous analyses and show that the part proportional to $k_{\mu} k_{\nu}/M^2$ must be modified near the resonance. We derive a mass shift which agrees with results obtained elsewhere by different methods. The modified form of a resonant heavy fermion propagator is also given.