Ultradense Tailored Vortex Pinning Arrays in Superconducting YBa₂Cu₃O_7−δThin Films Created by Focused He Ion Beam Irradiation for Fluxonics Applications

Abstract

Magnetic fields penetrate a type-II superconductor as magnetic flux quanta, called vortices. In a clean superconductor they arrange in a hexagonal lattice, while by adding periodic artificial pinning centers many other arrangements can be realized. Using the focused beam of a helium ion microscope we have fabricated periodic patterns of dense pinning centers with spacings as small as 70 nm in thin films of the cuprate superconductor YBa 2 Cu 3 O 7−δ . In these ultradense kagomé-like patterns, the voids lead to magnetic caging of vortices, resulting in unconventional commensurability effects that manifest themselves as peaks in the critical current and minima in the resistance vs applied magnetic field up to ∼ 0.4 T. The various vortex patterns at different magnetic fields are analyzed by molecular-dynamics simulations of vortex motion, and the magnetic-field dependence of the critical current is confirmed. These findings open the way for a controlled manipulation of vortices in cuprate superconductors by artificial sub-100 nm pinning landscapes.

Angle-dependent Magnetoresistance of an Ordered Bose Glass of Vortices in YBa2Cu3O7-δ Thin Films with a Periodic Pinning Lattice

“…The discoveries of artificial vortex ice [22] and anomalous metallic states [23,24] in YBCO are prominent examples. Even narrower patterns have been reported using focused light-ion irradiation [13,25,26].…”

“…Such a vortex-matching effect is illustrated in Figure 1a in a YBCO bridge subjected to focused 30 keV He + irradiation in a helium ion microscope. The fabrication process is described in detail elsewhere [13,25]. The irradiation produces a triangular lattice of CDs with distances a = (30 ± 0.6) nm.…”

Upper Frequency Limits for Vortex Guiding and Ratchet Effects

“…While the investigated system can be used as a rectifier up to 700 MHz, the relation between the upper frequency of the ratchet voltage and the nanostructure period, f r ∼ v/a, suggests that pinning arrays with a smaller period should result in higher f r . Since the current state of technology allows for the fabrication of sub-100 nmperiodic arrays of pinning sites [73], one can anticipate vortex diodes with cut-off frequencies above 10 GHz on the basis of superconducting films featuring small vortex core sizes in conjunction with high vortex velocities, such as e.g. superconducting cuprates [30].…”

Superconductivity in Nanosystems: A Fruitful Path to New Phenomenology in Quantum Materials

“…This includes nanosystems, such as, e.g., very thin films [ 1 ], tunnel–junction-based hybrid devices [ 2 ], superconductors with nanospaced defects or vortex pinning centers [ 3 ], interfacial superconductivity [ 4 ], etc.…”

“…Two articles in this Special Issue explore aspects related to the increase, by means of nanoengineering, of pinning centers for the superconducting quantum vortices. It is today well known that such pinning may increase the critical current, , which is of crucial importance, e.g., for high-field applications [ 3 , 5 , 8 ]. In their article, Ivan et al [ 9 ] conduct studies to demonstrate, among other aspects, that the frequency-dependent of their samples with self-assembled defects can be explained by using a new and simple, but effective, method involving AC susceptibility measurements.…”