Magnetic Vortices in Shaped Superconducting Mesocrystals
Magnetic vortices can be induced in a type-II superconductor with an applied magnetic field. A controlled number of vortices from zero to several hundred or more can be placed on a few-micron size crystal by adjusting the magnetic field strength. The magnetic vortices can serve as mesoscopic particles in few-body systems. Thus, superconducting mesocrystals enable comprehensive studies of few body thermodynamics and statistical mechanics, the evolution of complex mesoscopic patterns with particle number, melting of mesoscopic clusters of particles, disorder and relaxation in mesoscopic systems, and the transition from mesoscopic to bulk behavior. In addition to these general mesoscopic phenomena, these mesocrystals reveal qualitatively new superconducting phenomena at small scales which contrasts dramatically with conventional type-II bulk behavior.
We developed an electrochemical approach [Z. L. Xiao et al, J. Am. Chem. Soc. 126, 2316 (2004)] to synthesize superconducting lead (Pb) mesocrystals with novel shapes such as icosahedron, decahedron, hexagon and triangles and are developing vapor deposition methods to fabricate NbSe2 and MgB2 mesocrystals.
The vortex configurations in superconducting mesocrystals are probed with micro-Hall sensors [I. Lukyanchuk et al.,Nature Physics 11, 21 (2015)], micro-calorimeter and transport measurements with specially designed contact configurations.
