Abstract
Since the discovery of high-temperature superconductors (HTSs), most efforts of researchers have been focused on the fabrication of superconducting devices capable of immobilizing vortices, hence of operating at enhanced temperatures and magnetic fields. Recent findings that geometric restrictions may induce self-arresting hypervortices recovering the dissipation-free state at high fields and temperatures made superconducting strips a mainstream of superconductivity studies. Here we report on the geometrical melting of the vortex lattice in a wide YBCO submicron bridge preceded by magnetoresistance (MR) oscillations fingerprinting the underlying regular vortex structure. Combined magnetoresistance measurements and numerical simulations unambiguously relate the resistance oscillations to the penetration of vortex rows with intermediate geometrical pinning and uncover the details of geometrical melting. Our findings offer a reliable and reproducible pathway for controlling vortices in geometrically restricted nanodevices and introduce a novel technique of geometrical spectroscopy, inferring detailed information of the structure of the vortex system through a combined use of MR curves and large-scale simulations.
Highlights
Superconductors are materials in which below the superconducting transition temperature, Tc, electrons form so-called Cooper pairs, which are bosons, occupying the same lowest quantum state[1]
We unambigously relate the resistance oscillations with the sequential penetration of vortex rows, separated by regions of geometrical pinning, and reveal the fingerprints of the magnetoresistance that evidence vortex lattice melting in the strip
The peaks of the MR curves signal sequential penetration of the vortex rows into the strip[7], as confirmed by numerical simulations
Summary
Superconductors are materials in which below the superconducting transition temperature, Tc, electrons form so-called Cooper pairs, which are bosons, occupying the same lowest quantum state[1]. The collective motion of the Cooper-pair condensate occurs without scattering (the scattering would have served a mean for counting Cooper pairs), i.e., without power dissipation[2] This fundamental feature instrumental to technological applications of superconductivity is destroyed by magnetic vortices, tiny filaments of the magnetic field that penetrate the technologically important type-II superconductors. Carrying out simultaneous numerical simulations, magnetotransport measurements, and visualizing the vortex penetration and dynamics in the strip, we calibrate the fingerprints of the magnetoresistance. This enables us to directly juxtapose the observed features of the magnetoresistance with the microscopic behaviours of the vortex system. We detect melting of the vortex lattice and identify the flow of the pinned vortex liquid controlled by plastic deformation of the vortex matter[13]
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