Intermediate state in type-I superconductors: a new look at an old story*

Vladimir Kozhevnikov, Tulsa Community College, USA/ KU Leuven, Belgium.

Very rich physics of the intermediate state (IS) in type-I superconductors was recognized already at the first consideration of superconductivity as a new thermodynamic state of matter (Gorter and Casimir, 1934). Further studies of this state led to construction of major "pillars" of superconductivity theory, such as concepts of the surface tension, thermodynamic critical field and Andreev reflection. Properties of the IS are discussed in the first chapters of all superconductivity textbooks. However, although it may sound unexpectedly, many fundamental properties of the IS became known and understood only very recently.

A few years ago, attracted by the beauty of domain patterns and challenges of physics of the IS (also relevant to the mixed state in type-II superconductors) we revisited this state with use of state-of-the-art experimental techniques and the highest quality film samples**. In this talk I will present results of this study and introduce a new theoretical model for the first time consistently addressing all equilibrium properties of the IS. I will also present our most recent results of muSR probing of the IS, one more time reminding us that "There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy."

*Supported by NSF

** V. Kozhevnikov, R. J. Wijngaarden, J. de Wit and C. Van Haesendonck, PRB 89, 100503(R) (2014); V. Kozhevnikov and C. Van Haesendonck, PRB 90, 104519 (2014).