We study the general problem of a manifold of interacting elastic lines whose spatial correlations are strongly affected by the competition between random and ordered pinning. This is done through magneto-transport experiments with YBa2Cu3O7-d thin f
ilms that contain a periodic vortex pinning array created via masked ion irradiation, in addition to the native random pinning. The strong field-matching effects we observe suggest the prevalence of periodic pinning, and indicate that at the matching field each vortex line is bound to an artificial pinning site. However, the vortex-glass transition dimensionality, quasi-2D instead of the usual 3D, evidences reduced vortex-glass correlations along the vortex line. This is also supported by an unusual angular dependence of the magneto-resistance, which greatly differs from that of Bose-glass systems. A quantitative analysis of the angular magnetoresistance allows us to link this behaviour to the enhancement of the system anisotropy, a collateral effect of the ion irradiation.
We report on the realization of artificial ice using superconducting vortices in geometrically frustrated pinning arrays. This vortex ice shows two unique properties among artificial ice systems. The first comes from the possibility to switch the arr
ay geometric frustration on/off through temperature variations, which allows freezing and melting the vortex ice. The second is that the depinning and dynamics of the frozen vortex ice are insensitive to annealing, which implies that the ordered ground state is spontaneously approached. The major role of thermal fluctuations and the strong vortex-vortex interactions are at the origin of this unusual behavior.
We have developed a masked ion irradiation technique to engineer the energy landscape for vortices in oxide superconductors. This approach associates the possibility to design the landscape geometry at the nanoscale with the unique capability to adju
st depth of the energy wells for vortices. This enabled us to unveil the key role of vortex channeling in modulating the amplitude of the field matching effects with the artificial energy landscape, and to make the latter govern flux dynamics over an usually wide range of temperatures and applied fields.
We have investigated the electrodynamic properties of High-Tc strip-lines made by ion irradiation, in order to evaluate the potentialities of such a technology for RSFQ superconductor digital electronic. SQUID loops of different length and width have
been fabricated by ion bombardment of 70 nm thick films through e-beam lithographied shadow masks, and measured at different temperatures. The voltage modulations have been recorded by direct injection of a control current in the SQUIDs arms. The corresponding line inductances have been measured and compared with 3D simulations. A quantitative agreement has been obtained leading to typical values of 0.4 pH/microns without ground plane.
