1,901 research outputs found
Inelastic Confinement-Induced Resonances in Low-Dimensional Quantum Systems
A theoretical model is presented describing the confinement-induced
resonances observed in the recent loss experiment of Haller et al. [Phys. Rev.
Lett. 104, 153203 (2010)]. These resonances originate from possible molecule
formation due to the coupling of center-of-mass and relative motion. A
corresponding model is verified by ab initio calculations and predicts the
resonance positions in 1D as well as in 2D confinement in agreement with the
experiment. This resolves the contradiction of the experimental observations to
previous theoretical predictions.Comment: 5 pages, 4 figure
Theoretical description of two ultracold atoms in finite 3D optical lattices using realistic interatomic interaction potentials
A theoretical approach is described for an exact numerical treatment of a
pair of ultracold atoms interacting via a central potential that are trapped in
a finite three-dimensional optical lattice. The coupling of center-of-mass and
relative-motion coordinates is treated using an exact diagonalization
(configuration-interaction) approach. The orthorhombic symmetry of an optical
lattice with three different but orthogonal lattice vectors is explicitly
considered as is the Fermionic or Bosonic symmetry in the case of
indistinguishable particles.Comment: 19 pages, 5 figure
Resonances in ultracold dipolar atomic and molecular gases
A previously developed approach for the numerical treatment of two particles that are confined in a finite optical-lattice potential and interact via an arbitrary isotropic interaction potential has been extended to incorporate an additional anisotropic dipole–dipole interaction (DDI). The interplay of a model but realistic short-range Born–Oppenheimer potential and the DDI for two confined particles is investigated. A variation of the strength of the DDI leads to diverse resonance phenomena. In a harmonic confinement potential some resonances show similarities to s-wave scattering resonances while in an anharmonic trapping potential like the one of an optical lattice additional inelastic confinement-induced dipolar resonances occur. The latter are due to a coupling of the relative and center-of-mass motion caused by the anharmonicity of the external confinement.Peer Reviewe
Resonant optical control of the structural distortions that drive ultrafast demagnetization in CrO
We study how the color and polarization of ultrashort pulses of visible light
can be used to control the demagnetization processes of the antiferromagnetic
insulator CrO. We utilize time-resolved second harmonic generation
(SHG) to probe how changes in the magnetic and structural state evolve in time.
We show that, varying the pump photon-energy to excite either localized
transitions within the Cr or charge transfer states, leads to markedly
different dynamics. Through a full polarization analysis of the SHG signal,
symmetry considerations and density functional theory calculations, we show
that, in the non-equilibrium state, SHG is sensitive to {\em both} lattice
displacements and changes to the magnetic order, which allows us to conclude
that different excited states couple to phonon modes of different symmetries.
Furthermore, the spin-scattering rate depends on the induced distortion,
enabling us to control the timescale for the demagnetization process. Our
results suggest that selective photoexcitation of antiferromagnetic insulators
allows fast and efficient manipulation of their magnetic state.Comment: 7 pages, 5 figure
- …