<10/20(Tue) 16:00> Special talk by prof. T. Tamegai
Electromagnetic response of three-dimensional nanostructured superconductors are studied by using magneto-optical (MO) imaging method. In this talk, I will introduce two recent studies on three-dimensional nanostructured superconductors. The first topic is on the flux penetration and critical state in simple three-dimensional superconducting structures, such as orthogonal strips (crosses) and stacks of squares and rectangles. The critical state field profile is not a simple superposition of critical states in the two layers. Instead, flux penetration in one layer strongly modifies that of another layer. The second topic is on one of the simplest three-dimensional structures consisting of arrays of strips, where multiple layers of two-dimensional strip arrays are stacked with some shift between the neighboring layers [1-4]. We call these three-dimensional nanostructures “shifted strip arrays (SSAs)”. In SSAs, flux avalanches are observed when the overlap between layers is large even if the width of each strip is well below the threshold value. Various forms of avalanches either perpendicular or parallel to the strip are observed in SSAs when the overlap is large. How the number of layers up to six and other parameters affect the shape and behavior of flux avalanches in SSAs will be discussed.
 Y. Tsuchiya, Y. Mawatari, J. Ibuka, S. Tada, S. Pyon, S. Nagasawa, M. Hidaka, M. Maezawa, and T. Tamegai, Supercond. Sci. Technol. 26, 095004 (2013).
 T. Tamegai, Y. Tsuchiya, S. Tada, J. Ibuka, A. Mine, S. Pyon, Y. Mawatari, S. Nagasawa, M. Hidaka, and M. Maezawa, Physica C503, 62 (2014).
 S. Tada, Y. Tsuchiya, A. Mine, S. Pyon, T. Tamegai, S. Nagasawa, and M. Hidaka, Physics Procedia 58, 126 (2014).
 A. Mine, Y. Tsuchiya, S. Miyano, S. Pyon, T. Tamegai, S. Nagasawa, and M. Hidaka, to be published in Physica C (2015).