Riccardo Arpaia

Influence of topological edge states on the properties of Al/Bi2Se3/Al hybrid Josephson devices

In superconductor-topological insulator-superconductor hybrid junctions, the barrier edge states are expected to be protected against backscattering, to generate unconventional proximity effects, and, possibly, to signal the presence of Majorana fermions. The standards of proximity modes for these types of structures have to be settled for a neat identification of possible new entities. Through a systematic and complete set of measurements of the Josephson properties we find evidence of ballistic transport in coplanar Al-Bi2Se3-Al junctions that we attribute to a coherent transport through the topological edge state. The shunting effect of the bulk only influences the normal transport. This behavior, which can be considered to some extent universal, is fairly independent of the specific features of superconducting electrodes. A comparative study of Shubnikov-de Haas oscillations and scanning tunneling spectroscopy gave an experimental signature compatible with a two-dimensional electron transport channel with a Dirac dispersion relation. A reduction of the size of the Bi2Se3 flakes to the nanoscale is an unavoidable step to drive Josephson junctions in the proper regime to detect possible distinctive features of Majorana fermions.

Highly homogeneous YBCO/LSMO nanowires for photoresponse experiments

By using nanolithography and a soft etching procedure, we have realized YBa2Cu3O7-x/La0.7Sr0.3MnO3 (YBCO/LSMO) nanowires, with cross sections down to 100 x 50 nm(2) that ensure the cover age of areas up to 10 x 30 mu m(2). The LSMO layer acts as a capping for YBCO, minimizing the degradation of the superconducting properties taking place during the patterning; moreover, as a ferromagnetic manganite, it is expected to accelerate the relaxation dynamics of quasiparticles in YBCO, making such a system potentially attractive for applications in superconducting ultrafast optoelectronics. The reproducibility of the values of the critical current densities measured in different devices with the same geometry makes our nanowires ideal candidates for photoresponse experiments. First measurements have shown a satisfactory photoresponse from YBCO/LSMO devices.

Ultra low noise YBa2Cu3O7−δ nano superconducting quantum interference devices implementing nanowires

We present results on ultra low noise YBa

Phase transition of bismuth telluride thin films grown by MBE

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Transport properties of ultrathin YBa2Cu3O7-delta nanowires: A route to single-photon detection

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Improved noise performance of ultrathin YBCO Dayem bridge nanoSQUIDs

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Toward ultra high magnetic field sensitivity YBa2Cu3O7−δ nanowire based superconducting quantum interference devices

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Investigation into the growth and structure of thin-film solid solutions of iron-based superconductors in the FeSe0.92-FeSe0.5Te0.5 system

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Probing the phase diagram of cuprates with YBa2Cu3O7−δ thin films and nanowires

nano Superconducting QUantum Interference Devices (nanoSQUIDs). To realize such devices, we implemented high quality YBCO nanowires, working as weak links between two electrodes. We observe critical current modulation as a function of an externally applied magnetic field in the full temperature range below the transition temperature

Toward YBa2Cu3O7-δ nanoscale structures for hybrid devices

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