Commensurate and Incommensurate Vortex States Confined in Mesoscopic   Triangles of Weak Pinning Superconducting Thin Films
  We report on the direct observation of vortex states confined in equilateral and isosceles triangular dots of weak pinning amorphous superconducting thin films with a scanning superconducting quantum interference device microscope. The observed images illustrate not only pieces of a triangular vortex lattice as commensurate vortex states, but also incommensurate vortex states including metastable ones. We comparatively analyze vortex configurations found in different sample geometries and discuss the symmetry and stability of commensurate and incommensurate vortex configurations against deformations of the sample shape. 
Nobuhito Kokubo, Hajime Miyahara, Satoru Okayasu, and Tsutomu Nojima
cond-mat.supr-con cond-mat.mes-hall