Spontaneous vortex dynamics in superconducting FeTe thin films

Superconductivity is realized in Fe1+xTe (x=0.1-0.2) thin films grown on topological insulator Bi2Te3 by molecular beam epitaxy. A thorough analysis of the obtained transport data in terms of the vortex glass theory reveals the occurrence of a spontaneous vortex glass phase transition in the superconducting Fe1+xTe films. Such a phase transition is ascribed to the presence of excess Fe in Fe1+xTe, indicating the important role of excess Fe in the vortex dynamics of iron chalcogenide. Based on the transport data, a phase diagram of Fe1+xTe is also constructed.