14 research outputs found
Vortex ratchet induced by controlled edge roughness
We demonstrate theoretically and experimentally the generation of rectified mean vortex displacement resulting from a controlled difference between the surface barriers at the opposite borders of a superconducting strip. Our investigation focuses on Al superconducting strips where, in one of the two sample borders, a saw tooth-like array of micro-indentations has been imprinted.
The origin of the vortex ratchet effect is based on the fact that (i) the onset of vortex motion is mainly governed by the entrance/nucleation of vortices and (ii) the current lines bunching produced by the indentations facilitates the entrance/nucleation of vortices. Only for one current direction the indentations are positioned at the side of vortex entry and the onset of the resistive regime is lowered compared to the opposite current direction. This investigation points to the relevance of ubiquitous border effects typically neglected when interpreting vortex ratchet measurements on samples with arrays of local asymmetric pinning sites
Management Strategies to Adapt Alpine Space Forests to Climate Change Risks \u2013 An Introduction to the Manfred Project
Presentazione della struttura del progetto MANFRED, dei suoi obiettivi e dei metodi
Description of Case Study Areas for Deriving Management Strategies to Adapt Alpine Space Forests to Climate Change Risks
Descrizione delle aree di saggio scelte per lo studio dei principali fattori di rischio forestale legati ai cambiamenti climatici nelle Alpi
Thermal and quantum depletion of superconductivity in narrow junctions created by controlled electromigration
Superconducting nanowires currently attract great interest due to their application in
single-photon detectors and quantum-computing circuits. In this context, it is of fundamental
importance to understand the detrimental fluctuations of the superconducting order
parameter as the wire width shrinks. In this paper, we use controlled electromigration to
narrow down aluminium nanoconstrictions. We demonstrate that a transition from thermally
assisted phase slips to quantum phase slips takes place when the cross section becomes less
than 150 nm2 . In the regime dominated by quantum phase slips the nanowire loses its
capacity to carry current without dissipation, even at the lowest possible temperature. We
also show that the constrictions exhibit a negative magnetoresistance at low-magnetic fields,
which can be attributed to the suppression of superconductivity in the contact leads. These
findings reveal perspectives of the proposed fabrication method for exploring various
fascinating superconducting phenomena in atomic-size contacts