|The Eye of a Vortex: Dynamic phases of moving vortex lattices in a superconductor
Physics and Astronomy
|Eva Andrei, Rutgers University
Physics Lecture Hall
When an elastic medium is driven over a rough substrate it undergoes a transition from static to dynamic friction as a function of the driving force. Examples abound in nature: earthquakes, avalanches, fractures or vortex dynamics in superconductors. By following the onset of motion of a vortex lattice driven over a background of weak pinning centers we have obtained the dynamic phase diagram as a function of the force, magnetic field and temperature. Four phases are identified from the response to an applied force. The moving Bragg glass phase is marked by topological order with vortices following each other in distinct channels while maintaining the same number of neighbors. In this phase the onset of motion is characterized by a response time which is orders of magnitude slower than the intrinsic time scales. The other phases - moving smectic, plastic and liquid are distinguished by broken topological order and by fast, stepwise and instantaneous response respectively. I will describe the experiments that allowed us to determine the phase diagram and discuss the need for theoretical tools to study these out-of-equilibrium states.