In this 100th anniversary year of the discovery of superconductivity, physicists at the University of Massachusetts Amherst and Sweden’s Royal Institute of Technology have published a fully self-consistent theory of the new kind of superconducting behavior, Type 1.5, this month in the journal Physical Review B. In three recent papers, the authors report on their detailed investigations to show that a Type 1.5 superconducting state is indeed possible in a class of materials called multiband superconductors.
For years, most physicists believed that superconductors must be either Type I or Type II. Type 1.5 superconductivity is the subject of intense debate because until now there was no theory to connect the physics with micro-scale properties of real materials, say Egor Babaev of UMass Amherst, currently a fellow at the technology institute in Stockholm, with Mikhail Silaev, a postdoctoral researcher there. Their new papers now provide a theoretical framework to allow scientists to calculate conditions necessary for the appearance of Type 1.5 superconductivity, which exhibits characteristics of Types I and II previously thought to be antagonistic.