Browsing by Author "Montemurro, Domenico"

Now showing 1 - 5 of 5
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    Current-phase relation of a short multi-mode Bi2Se3 topological insulator nanoribbon Josephson junction with ballistic transport modes
    (Institute of Physics Publishing, 2023-06) Surendran, Ananthu P.; Montemurro, Domenico; Kunakova, Gunta; Palermo, Xavier; Niherysh, Kiryl; Trabaldo, Edoardo; Golubev, Dmitry S.; Andzane, Jana; Erts, Donats; Lombardi, Floriana; Bauch, Thilo; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Quantum Phenomena and Devices; Chalmers University of Technology; University of Latvia
    We used the asymmetric superconducting quantum interference device (SQUID) technique to extract the current phase relation (CPR) of a Josephson junction with a 3D-topological insulator (3D-TI) Bi2Se3 nanobelt as the barrier. The obtained CPR shows deviations from the standard sinusoidal CPR with a pronounced forward skewness. At temperatures below 200 mK, the junction skewness values are above the zero temperature limit for short diffusive junctions. Fitting of the extracted CPR shows that most of the supercurrent is carried by ballistic topological surface states (TSSs), with a small contribution of diffusive channels primarily due to the bulk. These findings are instrumental in engineering devices that can fully exploit the properties of the topologically protected surface states of 3D TIs.
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    Enhanced Josephson coupling in hybrid nanojunctions
    (American Physical Society, 2023-03) Montemurro, Domenico; Golubev, Dmitry S.; Kubatkin, Sergey; Tafuri, Francesco; Bauch, Thilo; Lombardi, Floriana; Chalmers University of Technology; Centre of Excellence in Quantum Technology, QTF; University of Naples Federico II; Department of Applied Physics
    We have fabricated NbN/Au nanogaps and bridged them with an Al superconductor using Ti as an interlayer. The nanodevices show a critical current density at 300 mK as high as 3×106A/cm2, which is 30% higher than that of Al nanowires with the same lateral dimensions as the NbN-based devices. The response of the critical current as a function of the external magnetic field clearly showed a Fraunhofer-like behavior, indicating a Josephson coupling between the NbN electrodes through the Al barrier. The superconducting transport evolves into different transport regimes as a function of the temperature. These findings demonstrate the importance of using superconducting barriers in hybrid nanodevices to achieve very high Josephson current in nanodevices of great relevance in superconducting circuits requiring high integration density.
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    Study of in-plane electrical transport anisotropy of a -axis oriented YBa2Cu3 O7-δ nanodevices
    (2017-05-04) Baghdadi, Reza; Arpaia, Riccardo; Stepantsov, Evgeny; Arzeo, Marco; Golubev, Dmitri; Montemurro, Domenico; Andersson, Eric; Bauch, Thilo; Lombardi, Floriana; Chalmers University of Technology; RAS - Shubnikov Institute of Crystallography; Department of Applied Physics
    In the present work, we report the growth of fully untwinned high-quality a-axis-oriented YBa2Cu3O7-δ films on (100) SrLaGaO4 substrates by using PrBa2Cu3O7-δ as a buffer layer. We also fabricated nanowires at different angles γ with respect to the [0,1,0] direction of the substrate and studied the in-plane anisotropy of the critical current density, which we explained by considering the anisotropy in the coherence length ξ and London penetration depth λL. Finally, half-integer Shapiro-like steps measured in slightly underdoped c-axis oriented (γ=90°) nanowires point towards a different transport regime, which could shed light on intriguing issues of high-critical-temperature superconductors.
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    Topological insulator nanoribbon Josephson junctions
    (American Institute of Physics, 2020-11-21) Kunakova, Gunta; Surendran, Ananthu P.; Montemurro, Domenico; Salvato, Matteo; Golubev, Dmitry; Andzane, Jana; Erts, Donats; Bauch, Thilo; Lombardi, Floriana; Chalmers University of Technology; University of Rome Tor Vergata; Centre of Excellence in Quantum Technology, QTF; University of Latvia; Department of Applied Physics
    We have used Bi 2 Se 3 nanoribbons, grown by catalyst-free physical vapor deposition to fabricate high quality Josephson junctions with Al superconducting electrodes. In our devices, we observe a pronounced reduction of the Josephson critical current density J c by reducing the width of the junction, which in our case corresponds to the width of the nanoribbon. Because the topological surface states extend over the entire circumference of the nanoribbon, the superconducting transport associated with them is carried by modes on both the top and bottom surfaces of the nanoribbon. We show that the J c reduction as a function of the nanoribbon width can be accounted for by assuming that only the modes traveling on the top surface contribute to the Josephson transport as we derive by geometrical consideration. This finding is of great relevance for topological quantum circuitry schemes since it indicates that the Josephson current is mainly carried by the topological surface states.
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    Transport properties of ultrathin YBa2Cu3 O7-δ nanowires
    (2017-08-25) Arpaia, Riccardo; Golubev, Dmitri; Baghdadi, Reza; Ciancio, Regina; DraŽić, Goran; Orgiani, Pasquale; Montemurro, Domenico; Bauch, Thilo; Lombardi, Floriana; Chalmers University of Technology; Department of Applied Physics; National Institute for Nuclear Physics; National Institute of Chemistry - Slovenia; University of Salerno
    We report on the growth and characterization of ultrathin YBa2Cu3O7-δ (YBCO) films on MgO (110) substrates, which exhibit superconducting properties at thicknesses down to 3 nm. YBCO nanowires, with thicknesses down to 10 nm and widths down to 65 nm, have also been successfully fabricated. The nanowires protected by a Au capping layer show superconducting properties close to the as-grown films and critical current densities, which are limited by only vortex dynamics. The 10-nm-thick YBCO nanowires without the Au capping present hysteretic current-voltage characteristics, characterized by a voltage switch which drives the nanowires directly from the superconducting to the normal state. We associate such bistability to the presence of localized normal domains within the superconductor. The presence of the voltage switch in ultrathin YBCO nanostructures, characterized by high sheet resistance values and high critical current values, makes our nanowires very attractive devices to engineer single-photon detectors.