Occam's Razor Cuts Down Superconductor Classifications

Highlight Date: 
02/11/2011
Display Section: 
Broad Audience Highlights
Article Title: 
Ginzburg-Landau Theory of Two-Band Superconductors: Absence of Type-1.5 Superconductivity
Author(s): 
V. G. Kogan and J. Schmalian
Article Link: 
Journal Name: 
Physical Review B
Volume: 
83
Year: 
2011
Page Number(s): 
054515
Highlight Image: 
Highlight Text: 

Researchers have wrestled with the question of whether or not the newest superconducting materials fit within the traditional classifications. Superconductors can be divided into Type 1 and Type 2, depending on how they behave in a magnetic field. However, magnesium diboride was discovered to have characteristics of both categories and has been dubbed “Type 1.5”. Drawing on the fundamentals of Ginzburg-Landau theory, the basis of the two original types, a combination of theory and simulation has determined that a new class is not warranted. Close to the superconducting transition temperature (where the Ginzburg-Landau theory is valid), the energy of the interface between a normal and a superconducting region is described by the same universal function for Type 1 and Type 2 superconductors and also those that behave like both. This makes the idea of Type 1.5 superconductivity unnecessary within the Ginzburg-Landau theory. The behavior of magnesium diboride can be understood in terms of Type 2 superconductivity.