title: Imaging atomic-scale effects of high-energy ion irradiation on superconductivity and vortex pinning in Fe(Se,Te).
abstract: Maximizing the sustainable supercurrent density, J C, is crucial to high-current applications of superconductivity. To achieve this, preventing dissipative motion of quantized vortices is key. Irradiation of superconductors with high-energy heavy ions can be used to create nanoscale defects that act as deep pinning potentials for vortices. This approach holds unique promise for high-current applications of iron-based superconductors because J C amplification persists to much higher radiation doses than in cuprate superconductors without significantly altering the superconducting critical temperature. However, for these compounds, virtually nothing is known about the atomic-scale interplay of the crystal damage from the high-energy ions, the superconducting order parameter, and the vortex pinning processes. We visualize the atomic-scale effects of irradiating FeSe x Te1-x with 249-MeV Au ions and find two distinct effects: compact nanometer-sized regions of crystal disruption or "columnar defects," plus a higher density of single atomic site "point" defects probably from secondary scattering. We directly show that the superconducting order is virtually annihilated within the former and suppressed by the latter. Simultaneous atomically resolved images of the columnar crystal defects, the superconductivity, and the vortex configurations then reveal how a mixed pinning landscape is created, with the strongest vortex pinning occurring at metallic core columnar defects and secondary pinning at clusters of point-like defects, followed by collective pinning at higher fields.
authors.affiliation: Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA. ; Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA. ; Laboratoire de Physique des Solides, Universite Paris-Sud, 91405 Orsay, France.
authors.forename: Freek
authors.initials: F
authors.lastname: Massee
authors.affiliation: Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA. ; Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Peter Oliver
authors.initials: PO
authors.lastname: Sprau
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Yong-Lei
authors.initials: YL
authors.lastname: Wang
authors.affiliation: Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA. ; Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA. ; School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK. ; Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA.
authors.forename: J C Séamus
authors.initials: JC
authors.lastname: Davis
authors.affiliation: Department of Applied Science and Technology, Politecnico di Torino, 10129 Torino, Italy. ; Istituto Nazionale di Fisica Nucleare, Sezione di Torino, 10125 Torino, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Ghigo
authors.affiliation: Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Genda D
authors.initials: GD
authors.lastname: Gu
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Wai-Kwong
authors.initials: WK
authors.lastname: Kwok
keywords: Critical Current by Design; High Energy Ion Irradiation; Iron-based Superconductivity; Spectroscopic Imaging Scanning Tunneling Microscopy; Vortex Pinning