Scanning Hall probe microscopy of vortex matter in artificial type-1.5 and low-k superconductors.
The proposed project aims at deepening our understanding of the intricate vortex-vortex interactions that determine the vortex patterns and related superconducting properties in type- 1.5 and low-k superconductors. It is well known that superconductors can be categorized into type-I and type-II by the Ginzburg-Landau parameter k. While in type-I superconductors, vortices experience a short-range attractive interaction leading to the formation of the intermediate state, in type-II superconductors the mixed state with triangular lattice is formed due to vortex repulsion. However, apart from the well known intermediate state and mixed state, vortex interactions can also be non-monotonic, such as in the recently discovered type-1.5 superconductors and the low-k superconductors. Compared with intensively studied type-I and type-II superconductivity, a thorough understanding of vortex interactions and mechanisms in type-1.5 and low-k superconductors is still lacking. A state of the art technique, the scanning Hall probe microscopy, will be exploited to investigate the vortex structures and dynamics in artificial type-1.5 superconducting hybrid structures and a series of superconductors with k crossing the dual point ~0.71. Our study will not only shed new light on vortex matter with non-monotonic interactions but also provide a platform to investigate other modulated systems where the access to manipulate system parameters is much more difficult.