C-axis Optical Sum Rule in Josephson Coupled Vortex State

Observed violations of the $c$-axis optical sum rule can give important information on deviations from in-plane Fermi liquid behavior and on the nature of interlayer coupling between adjacent copper oxide planes. Application of a magnetic field perpendicular to these planes is another way to probe in-plane dynamics. We find that the optical sum rule is considerably modified in the presence of the $c$-axis magnetic field. Interlayer correlation of pancake vortices is involved in the sum rule modification; however, details of the vortex distribution in the plane are less important.Comment: one figure. To be published in PRB (Sep. 20001

Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction

We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a 87Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results

A Mesoscopic Blue-detuned Light Ring for Bose-Einstein Condensates Based on Conical Refraction

Conical refraction (CR) is an optical phenomenon observed in biaxial crystals (BCs) that has been a subject of renewed interest since the last decade [1], despite being predicted by W.R. Hamilton in 1832. CR occurs when a light beam propagates along one of the optic axes of a biaxial crystal with birefringence R0 = l·α, where l is the length of the crystal and α is its conicity [2]. Under such conditions, an input focused Gaussian beam with beam waist radius w0, is transformed into two concentric bright rings at the focal image plane of the system, as long as the condition R0 >> w0 is satisfied. These bright rings are separated by a thin ring of null intensity known as the Poggendorff dark ring (PDR), see Fig. 1