Search results for "Optica"
showing 10 items of 7696 documents
The electron gas with short coherence length pairs: how to approach the stronger coupling limit?
2001
Abstract The attractive Hubbard model is investigated in 2D using a T -matrix approach. In a self-consistent calculation pairs as infinite lifetime Bosons only exist in the atomic limit and therefore a Fermi surface can be investigated also in the stronger coupling regime. A heavy quasiparticle peak with a weak dispersion crosses the Fermi surface at k F whereas light, single particle excitations do only exist far away from the Fermi surface. At low temperatures there seem to exist different self-consistent solutions. In one of them a pseudogap opens even in the integrated density of states. In the present work accurate k -dependent and k -integrated spectral quantities for a 2D finite latt…
Magnetic phase diagram of the anisotropic multi-band Hubbard model
2007
Using quantum Monte Carlo (QMC) simulations we determine the magnetic phase diagram of the anisotropic two-band Hubbard model within the dynamical mean-field theory (DMFT) in the important intermediate-coupling regime. We compare the QMC predictions with exact results from second-order weak-and strong-coupling perturbation theory. We find that the orbital-selective Mott transition (OSMT), which occurs in the fully frustrated case, is completely hidden in the antiferromagnetic (AF) ground state of the model. On the basis of our results, we discuss possible mechanisms of frustration. We also demonstrate the close relationship of the physics of the two-band Hubbard model in the orbital-selecti…
Quantum signatures in the dynamics of two dipole-dipole interacting soft dimers
2006
The quantum covariances of physically transparent pairs of observables relative to two dimers hosted in a solid matrix are exactly investigated in the temporal domain. Both dimers possess fermionic and bosonic degrees of freedom and are dipolarly coupled. We find out and describe clear signatures traceable back to the presence and persistence of quantum coherence in the time evolution of the system. Manifestations of a competition between intramolecular and intermolecular energy migration mechanisms are brought to light. The experimental relevance of our results is briefly commented.
Phase sticking in one-dimensional Josephson junction chains
2013
Published version of an article in the journal: Physical Review B - Condensed Matter and Materials Physics. Also available from the publisher at: http://dx.doi.org/10.1103/PhysRevB.88.104501 We studied current-voltage characteristics of long one-dimensional Josephson junction chains with Josephson energy much larger than charging energy, EJ EC. In this regime, typical I-V curves of the samples consist of a supercurrent-like branch at low-bias voltages followed by a voltage-independent chain current branch, Ichain at high bias. Our experiments showed that Ichain is not only voltage-independent but it is also practically temperature-independent up to T=0.7TC. We have successfully model the tr…
Trapping of ultracold atoms in a hollow-core photonic crystal fiber
2008
Ultracold sodium atoms have been trapped inside a hollow-core optical fiber. The atoms are transferred from a free space optical dipole trap into a trap formed by a red-detuned gaussian light mode confined to the core of the fiber. We show that at least 5% of the atoms held initially in the free space trap can be loaded into the core of the fiber and retrieved outside.
Towards nonlinear optics with cold Rydberg atoms inside a hollow core fiber
2015
We present an experimental setup for studying strongly nonlinear light-matter interactions using cold atoms inside a hollow core fiber. A Rydberg EIT process can potentially be used to generate strong and tunable effective photon-photon interactions.
Néel Transition of Lattice Fermions in a Harmonic Trap: A Real-Space Dynamic Mean-Field Study
2010
We study the magnetic ordering transition for a system of harmonically trapped ultracold fermions with repulsive interactions in a cubic optical lattice, within a real-space extension of dynamical mean-field theory. Using a quantum Monte Carlo impurity solver, we establish that antiferromagnetic correlations are signaled, at strong coupling, by an enhanced double occupancy. This signature is directly accessible experimentally and should be observable well above the critical temperature for long-range order. Dimensional aspects appear less relevant than naively expected.
Exploring Quantum Matter with Ultracold Atoms in Optical Lattices
2005
Publisher Summary This chapter explores quantum matter with ultracold atoms in optical lattices. The chapter focuses on bosonic atoms in optical lattices and on the regime where strong correlations between the atoms become important. In the interaction of atoms with coherent light fields, two fundamental forces arise. The Doppler force is dissipative in nature and can be used to efficiently laser cool a gas of atoms and relies on the radiation pressure together with spontaneous emission. The dipole force creates a purely conservative potential in which the atoms can move. No cooling can be realized with this dipole force, however if the atoms are cold enough initially, they may be trapped i…
Fermionic transport and out-of-equilibrium dynamics in a homogeneous Hubbard model with ultracold atoms
2012
The transport measurements of an interacting fermionic quantum gas in an optical lattice provide a direct experimental realization of the Hubbard model—one of the central models for interacting electrons in solids—and give insights into the transport properties of many-body phases in condensed-matter physics.
Counting atoms using interaction blockade in an optical superlattice.
2008
We report on the observation of an interaction blockade effect for ultracold atoms in optical lattices, analogous to Coulomb blockade observed in mesoscopic solid state systems. When the lattice sites are converted into biased double wells, we detect a discrete set of steps in the well population for increasing bias potentials. These correspond to tunneling resonances where the atom number on each side of the barrier changes one by one. This allows us to count and control the number of atoms within a given well. By evaluating the amplitude of the different plateaus, we can fully determine the number distribution of the atoms in the lattice, which we demonstrate for the case of a superfluid …