Paving the way for smaller and more efficient devices, a superconducting sheet just two atoms thick has been created at The University of Texas at Austin by Dr. Ken Shih and colleagues [Shengyong Qin, et al., DOI: 10.1126/science.1170775]. This is the thinnest superconducting sheet ever produced in a metal layer. The ultra-thin material, of lead, is a highly uniform crystalline structure that confines electrons, in ‘Cooper pairs’, to move through the material in two dimensions or a single, quantum channel without a power source.
Despite the constrained movement, the lead is a good superconductor. “We can make this film, and it has perfect crystalline structure, more perfect than most thin films made of other materials,” says Ken Shih. Advanced materials synthesis techniques were used to deposit the lead onto a thin silicon surface, the process providing a layer free from impurities and having a regularised structure. Results show that binding of Cooper pairs remains strongly affected by the substrate and its interaction with the superconducting material.
Previous studies of 2D superconductivity have shown 2D wave function but with an underlying electron behaviour remains in 3D. However, advancements in the growth of epitaxial superconductor thin films with control over crystallinity have enabled the production of ultra-thin films on substrates. Tunneling spectroscopy was used by Shih’s team to determine the thickness and the atomic structure, two distinct patterns emerging with different superconducting properties – in particular, the temperature at which superconductivity is evident.
Shih is hopeful that the processes used to produce the two-atom thick layer will lead to further developments that determine the role of the substrate in superconductivity properties and that commercial applications will ensue, in devices such as particle accelerators, quantum interface devices and MRI machines. “To be able to control this material – to shape it into new geometries – and explore what happens is very exciting, my hope is that this superconductive surface will enable one to build devices and study new properties of superconductivity,” he concludes.