Pulsed Laser Deposition of Rocksalt Magnetic Binary Oxides

Here we systematically explore the use of pulsed laser deposition technique (PLD) to grow three basic oxides that have rocksalt structure but different chemical stability in the ambient atmosphere: NiO (stable), MnO (metastable) and EuO (unstable). By tuning laser fluence, an epitaxial single-phase nickel oxide thin-film growth can be achieved in a wide range of temperatures from 10 to 750 {\deg}C. At the lowest growth temperature, the out-of-plane strain raises to 1.5%, which is five times bigger than that in a NiO film grown at 750 {\deg}C. MnO thin films that had long-range ordered were successfully deposited on the MgO substrates after appropriate tuning of deposition parameters. The growth of MnO phase was strongly influenced by substrate temperature and laser fluence. EuO films with satisfactory quality were deposited by PLD after oxygen availability had been minimized. Synthesis of EuO thin films at rather low growth temperature prevented thermally-driven lattice relaxation and allowed growth of strained films. Overall, PLD was a quick and reliable method to grow binary oxides with rocksalt structure in high quality that can satisfy requirements for applications and for basic research

Coexisting multiple dynamic states generated by magnetic field in Bi-2212 stacked Josephson junctions

Josephson vortices in naturally stacked Bi-2212 tunneling junctions display rich dynamic behavior that derives from the coexistence of three basic states: static Josephson vortex lattice, coherently moving lattice, and incoherent quasiparticle tunneling state. Rich structure of hysteretic branches observed in the current-voltage characteristics can be understood as combinatorial combinations of these three states which are realized in different junctions and evolve separately with magnetic field and bias current. In particular, the multiple Josephson-vortex-flow branches at low bias currents arise from the individual depinning of Josephson vortex rows in each junction.Comment: Submitted to Europhysics Letter

Potassium-doped BaFe2As2 superconducting thin films with a transition temperature of 40 K

We report the growth of potassium-doped BaFe2As2 thin films, where the major charge carriers are holes, on Al2O3 (0001) and LaAlO3 (001) substrates by using an ex-situ pulsed laser deposition technique. The measured Tc's are 40 and 39 K for the films grown on Al2O3 and LaAlO3, respectively and diamagnetism indicates that the films have good bulk superconducting properties below 36 and 30 K, respectively. The X-ray diffraction patterns for both films indicated a preferred c-axis orientation, regardless of the substrate structures of LaAlO3 and Al2O3. The upper critical field at zero temperature was estimated to be about 155 T.Comment: 6 pages including 3 figure

Graphene-based Josephson junction single photon detector

We propose to use graphene-based Josephson junctions (gJjs) to detect single photons in a wide electromagnetic spectrum from visible to radio frequencies. Our approach takes advantage of the exceptionally low electronic heat capacity of monolayer graphene and its constricted thermal conductance to its phonon degrees of freedom. Such a system could provide high sensitivity photon detection required for research areas including quantum information processing and radio-astronomy. As an example, we present our device concepts for gJj single photon detectors in both the microwave and infrared regimes. The dark count rate and intrinsic quantum efficiency are computed based on parameters from a measured gJj, demonstrating feasibility within existing technologies.Comment: 11 pages, 6 figures, and 1 table in the main tex