title: Probing dynamics and pinning of single vortices in superconductors at nanometer scales.
abstract: The dynamics of quantized magnetic vortices and their pinning by materials defects determine electromagnetic properties of superconductors, particularly their ability to carry non-dissipative currents. Despite recent advances in the understanding of the complex physics of vortex matter, the behavior of vortices driven by current through a multi-scale potential of the actual materials defects is still not well understood, mostly due to the scarcity of appropriate experimental tools capable of tracing vortex trajectories on nanometer scales. Using a novel scanning superconducting quantum interference microscope we report here an investigation of controlled dynamics of vortices in lead films with sub-Angstrom spatial resolution and unprecedented sensitivity. We measured, for the first time, the fundamental dependence of the elementary pinning force of multiple defects on the vortex displacement, revealing a far more complex behavior than has previously been recognized, including striking spring softening and broken-spring depinning, as well as spontaneous hysteretic switching between cellular vortex trajectories. Our results indicate the importance of thermal fluctuations even at 4.2 K and of the vital role of ripples in the pinning potential, giving new insights into the mechanisms of magnetic relaxation and electromagnetic response of superconductors.
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: L
authors.initials: L
authors.lastname: Embon
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Anahory
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Suhov
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: D
authors.initials: D
authors.lastname: Halbertal
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: J
authors.initials: J
authors.lastname: Cuppens
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Yakovenko
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Uri
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Myasoedov
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: M L
authors.initials: ML
authors.lastname: Rappaport
authors.affiliation: Department of Physics, University of Colorado Denver, Denver, 80217, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Huber
authors.affiliation: Department of Physics, Old Dominion University, Norfolk, VA 23529-0116, USA.
authors.forename: A
authors.initials: A
authors.lastname: Gurevich
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: E
authors.initials: E
authors.lastname: Zeldov