Superconducting nanostructures in 3D

The creation of three-dimensional superconducting nanostructures enables local control of the superconducting state.

(Nanowerk News) The move from two to three dimensions can have a significant impact on how a system behaves, whether it is folding a sheet of paper into a paper aeroplane or twisting a wire into a helical spring. At the nanoscale, one thousand times smaller than a human hair, one approaches the fundamental lengthscales of, for example, quantum materials. At these lengthscales, the patterning of nanogeometries can lead to changes in the material properties itself – and when one moves to three dimensions, there come new ways to tailor functionalities, by breaking symmetries, introducing curvature, and creating interconnected channels. Despite these prospects, one of the main challenges remains: how to realise such complex 3D geometries, at the nanoscale, in quantum materials? In a new study, an international team led by researchers at the Max Planck Institute for Chemical Physics of Solids have created three dimensional superconducting nanostructures using a technique similar to a nano-3D printer. They achieved local control of the superconducting state in a 3D bridge-like superconductor, and could even demonstrate the motion of superconducting vortices – nanoscale defects in the superconducting state – in three dimensions. The work has been published in the journal Advanced Functional Materials (“Reconfigurable Three-Dimensional Superconducting Nanoarchitectures”). Scanning electron microscope image of a three dimensional superconducting nanostructure (nanobridge) deposited using direct-write 3D nanoprinting. (Image: MPI CPfS / E. Zhakina) Superconductors are materials that are renowned for their ability to exhibit zero electrical resistance and expel magnetic fields. This behaviour arises from the formation of so-called Cooper pairs: bound pairs of electrons that move coherently through the material without scattering. “One of the main challenges involves gaining control over this superconducting state at the nanoscale, which is key for the exploration of novel effects, and the future development of technological devices” explains Elina Zhakina, postdoctoral researcher at the Max Planck Institute for Chemical Physics of Solids. When patterning superconductors in 3D nanogeometries, the international team, involving researchers from Germany and Austria, were able to locally control the superconducting state – i.e. “switching off” the superconductivity in different parts of the nanostructure. This coexistence of superconducting and “normal” states can lead to quantum mechanical effects, such as so-called weak links, used for example for ultra-sensitive sensing. However, until now such control has typically required the design of structures, for example in planar thin films, where the coexistence of states is predetermined. “We found that it is possible to switch on and off the superconducting state in different parts of the threedimensional nanostructure, simply by rotating the structure in a magnetic field” said Claire Donnelly, Lise Meitner Group leader at the Max Planck Institute for Chemical Physics of Solids. “In this way, we were able to realise a “reconfigurable” superconducting device!”. This realization of reconfigurable functionality offers a new platform for building adaptive or multi-purpose superconducting components. This, along with the ability to propagate defects of the superconducting state, opens the door to complex superconducting logic and neuromorphic architectures setting the stage for a new generation of reconfigurable superconducting technologies.