Strong interconversion of non-polar phonons and Josephson plasma oscillations induced by equilibrium Josephson currents in high T_c superconductors

We analyze consequences of dynamical modulations of Josephson current by non-polar lattice mode in the Josephson junction barrier. In the high $T_c$ junctions, the effect of such modulations can be anomalously strong due to the proximity of the insulating barrier to the superconducting state. Accordingly, the interconversion of sound (as well as other non-polar phonons) and the Josephson plasma oscillations mediated by stationary Josephson currents, which may be present in the junction due to various reasons, becomes possible. We suggest that this effect can be employed for imaging of the stationary Josephson currents. Estimates of the effect are given.Comment: 11 RevTeX pages, no figure

Mobile π−\pi-kinks and half-integer zero-field-like steps in highly discrete alternating 0−π0-\pi Josephson junction arrays

The dynamics of a one-dimensional, highly discrete, linear array of alternating $0-$ and $\pi-$ Josephson junctions is studied numerically, under constant bias current at zero magnetic field. The calculated current - voltage characteristics exhibit half-integer and integer zero-field-like steps for even and odd total number of junctions, respectively. Inspection of the instantaneous phases reveals that, in the former case, single $\pi-$kink excitations (discrete semi-fluxons) are supported, whose propagation in the array gives rise to the $1/2-$step, while in the latter case, a pair of $\pi-$kink -- $\pi-$antikink appears, whose propagation gives rise to the $1-$step. When additional $2\pi-$kinks are inserted in the array, they are subjected to fractionalization, transforming themselves into two closely spaced $\pi-$kinks. As they propagate in the array along with the single $\pi-$kink or the $\pi-$kink - $\pi-$antikink pair, they give rise to higher half-integer or integer zero-field-like steps, respectively.Comment: 7 pages, 8 figures, submitted to Supercond. Sci. Techno

Induced paramagnetic states by localized π\pi -loops in grain boundaries

Recent experiments on high-temperature superconductors show paramagnetic behavior localized at grain boundaries (GB). This paramagnetism can be attributed to the presence unconventional d-wave induced $\pi$-junctions. By modeling the GB as an array of $\pi$ and conventional Josephson junction we determine the conditions of the occurrence of the paramagnetic behavior.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let

Voting 'against all' in postcommunist Russia

Since the early 1990s voters in Russia (and most of the other post-Soviet republics) have been offered the opportunity to vote ‘against all’ parties and candidates. Increasing numbers have done so. The evidence of two post-election surveys indicates that ‘against all’ voters are younger than other voters, more urban and more highly educated. They do not reject liberal democracy, but are critical of the contemporary practice of Russian politics and find no parties that adequately reflect their views. With the ending of the ‘against all’ facility in 2006 and other changes in the Russian electoral system under the Putin presidency, levels of turnout are likely to fall further and the protest vote will seek other outlets within or outside the parliamentary system

Quantum state engineering with Josephson-junction devices

We review recent theoretical and experimental progress in quantum state engineering with Josephson junction devices. The concepts of quantum computing have stimulated an increased activity in the field. Either charges or phases (fluxes) of the Josephson systems can be used as quantum degrees of freedom, and their quantum state can be manipulated coherently by voltage and current pulses. They thus can serve as qubits, and quantum logic gates can be performed. Their phase coherence time, which is limited, e.g., by the electromagnetic fluctuations in the control circuit, is long enough to allow a series of these manipulations. The quantum measurement process performed by a single-electron transistor, a SQUID, or further nanoelectronic devices is analyzed in detail.Comment: An article prepared for Reviews of Modern Physics, 46 pages, 23 figure

Theory of charge transport in diffusive normal metal / unconventional singlet superconductor contacts

We analyze the transport properties of contacts between unconventional superconductor and normal diffusive metal in the framework of the extended circuit theory. We obtain a general boundary condition for the Keldysh-Nambu Green's functions at the interface that is valid for arbitrary transparencies of the interface. This allows us to investigate the voltage-dependent conductance (conductance spectrum) of a diffusive normal metal (DN)/ unconventional singlet superconductor junction in both ballistic and diffusive cases. For d-wave superconductor, we calculate conductance spectra numerically for different orientations of the junctions, resistances, Thouless energies in DN, and transparencies of the interface. We demonstrate that conductance spectra exhibit a variety of features including a $V$-shaped gap-like structure, zero bias conductance peak (ZBCP) and zero bias conductance dip (ZBCD). We show that two distinct mechanisms: (i) coherent Andreev reflection (CAR) in DN and (ii) formation of midgap Andreev bound state (MABS) at the interface of d-wave superconductors, are responsible for ZBCP, their relative importance being dependent on the angle $\alpha$ between the interface normal and the crystal axis of d-wave superconductors. For $\alpha=0$, the ZBCP is due to CAR in the junctions of low transparency with small Thouless energies, this is similar to the case of diffusive normal metal / insulator /s-wave superconductor junctions. With increase of $\alpha$ from zero to $\pi/4$, the MABS contribution to ZBCP becomes more prominent and the effect of CAR is gradually suppressed. Such complex spectral features shall be observable in conductance spectra of realistic high-$T_c$ junctions at very low temperature

Photopatterned antibodies for selective cell attachment

We present a phototriggerable system that allows for the spatiotemporal controlled attachment of selected cell types to a biomaterial using immobilized antibodies that specifically target individual cell phenotypes.o-Nitrobenzyl caged biotin was used to functionalize chitosan membranes and mediate site-specific coupling of streptavidin and biotinylated antibodies after light activation. The ability of this system to capture and immobilize specific cells on a surface was tested using endothelial-specific biotinylated antibodies and nonspecific ones as controls. Homogeneous patterned monolayers of human umbilical vein endothelial cells were obtained on CD31-functionalized surfaces. This is a simple and generic approach that is applicable to other ligands, materials, and cell types and shows the flexibility of caged ligands to trigger and control the interaction between cells and biomaterials.We thank Martina Knecht (MPIP) for help with the synthesis of caged biotin and Dr. Ron Unger and Prof. C. J. Kirkpatrick (University Clinic Mainz, RepairLab) for providing HUVECs. C.A.C. acknowledges funding support from the Portuguese Foundation for Science and Technology (FCT) (fellowship SFRH/BD/61390/2009) and from the International Max-Planck Research School in Mainz. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. REGPOT-CT2012-316331-POLARIS