Authors: Bernd Aichner, Benedikt Müller, Max Karrer, Vyacheslav R. Misko, Fabienne Limberger, Kristijan L. Mletschnig, Meirzhan Dosmailov, Johannes D. Pedarnig, Franco Nori, Reinhold Kleiner, Dieter Koelle, and Wolfgang Lang
ACS Appl. Nano Mater. 2019, 2, 5108−5115
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 addition of 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 YBa2Cu3O7−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 versus applied magnetic ﬁeld up to∼0.4T. 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.