Impact of the transport supercurrent on the Josephson effect

We study the weak link between current-carrying superconductors, both conventional and d-wave. The state of the system is controlled by two parameters: the order parameter phase difference $\phi$ and the superfluid velocity $v_{s}$, which parameterizes the parallel to the boundary transport supercurrent which is injected externally. The low-temperature current-phase relations are derived. We consider two models of weak links: a constriction between two conventional superconductors and a plane boundary between two differently orientated d-wave superconductors. We show that for some relation between $\phi$ and $v_{s}$ quasiparticles create the current along the boundary which flows in the direction opposite to the transport supercurrent.Comment: 5 pages, 3 figures; submitted for publication in Proceedings of MS+S2004 symposium (without Sec.V and the last part of Sec.III

Resonant effects in the strongly driven phase-biased Cooper-pair box

We study the time-averaged upper level occupation probability in a strongly driven two level system, particularly its dependence on the driving amplitude, frequency and the energy level separation. In contrast to the case of weak driving, when the positions of the resonances almost do not depend on the driving amplitude, in the case of the strong diving their positions are strongly amplitude-dependent. We study these resonances in the concrete system -- the strongly driven phase-biased Cooper-pair box, which is considered to be weakly coupled to the tank circuit

Capture of slow antiprotons by helium atoms

A consistent quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. For the four-body scattering wave function, corresponding to the initial state, as well as for the antiprotonic helium wave function, appearing in the final tate, adiabatic approximations was used. Calculations were carried out for a wide range of antiprotonic helium states and incident energies of the antiproton. Obtained energy dependances of some cross sections show a rich low energy structure.Comment: 16 pages, 8 color pictures; the text, the bibliography, and the pictures were slightly correcte

Exact calculations of a quasi-bound state in the KˉKˉN\bar{K} \bar{K} N system

Dynamically exact calculations of a quasi-bound state in the $\bar{K}\bar{K}N$ three-body system are performed using Faddeev-type AGS equations. As input two phenomenological and one chirally motivated $\bar{K}N$ potentials are used, which describe the experimental information on the $\bar{K}N$ system equally well and produce either a one- or two-pole structure of the $\Lambda(1405)$ resonance. For the $\bar{K}\bar{K}$ interaction separable potentials are employed that are fitted to phase shifts obtained from two theoretical models. The first one is a phenomenological $\bar{K}\bar{K}$ potential based on meson exchange, which is derived by SU(3) symmetry arguments from the J\"ulich $\pi \pi - \bar{K} K$ coupled-channels model. The other interaction is a variant of the first one, which is adjusted to the $KK$ s-wave scattering length recently determined in lattice QCD simulations. The position and width of the $\bar{K}\bar{K}N$ quasi-bound state is evaluated in two ways: (i) by a direct pole search in the complex energy plane and (ii) using an "inverse determinant" method, where one needs to calculate the determinant of the AGS system of equations only for real energies. A quasi-bound state is found with binding energy $B_{\bar{K}\bar{K}N} = 12 - 26$ MeV and width $\Gamma_{\bar{K}\bar{K}N} = 61 - 102$ MeV, which could correspond to the experimentally observed $\Xi(1950)$ state.Comment: 18 pages, 2 figures, 2 table