scanning-squid-study-of-vortex-manipulation-by-local-contact

Scanning SQUID Study of Vortex Manipulation by Local Contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

Libraries and Information System of Bar-Ilan University

Bar-Ilan University

Manipulating individual vortices in a deterministic way is challenging; ideally, manipulation should be effective, local, and tunable in strength and location. Here, we show that vortices respond to local mechanical stress applied in the vicinity of the vortex. We utilized this interaction to move individual vortices in thin superconducting films via local mechanical contact without magnetic field or current. We used a scanning superconducting quantum interference device to image vortices and to apply local vertical stress with the tip of our sensor. Vortices were attracted to the contact point, relocated, and were stable at their new location. We show that vortices move only after contact and that more effective manipulation is achieved with stronger force and longer contact time. Mechanical manipulation of vortices provides a local view of the interaction between strain and nanomagnetic objects as well as controllable, effective, and reproducible manipulation technique.

Mechanical Control of Individual Superconducting Vortices.

The metal-insulator transition (MIT) properties of correlated oxides thin films, such as VO2, are dramatically affected by strain induced at the interface with the substrate, which usually changes with deposition thickness. For VO2 grown on r-cut sapphire, there is a minimum deposition thickness required for a significant MIT to appear, around 60 nm. We show that in these thicker films an interface layer develops, which accompanies the relaxation of film strain and enhanced electronic transition. If these interface dislocations are stable at room temperature, we conjectured, a new route opens to control thickness of VO2 films by postdeposition thinning of relaxed films, overcoming the need for thickness-dependent strain-engineered substrates. This is possible only if thinning does not alter the films' electronic properties. We find that wet etching in a dilute NaOH solution can effectively thin the VO2 films, which continue to show a significant MIT, even when etched to 10 nm, for which directly deposited films show nearly no transition. The structural and chemical composition were not modified by the etching, but the grain size and film roughness were, which modified the hysteresis width and magnitude of the MIT resistance change.

Shai Wissberg

Department of Physics and Institute of Nanotechnology and Advanced Materials

Libraries and Information System of Bar-Ilan University

Scanning SQUID Study of Vortex Manipulation by Local Contact