Unusual current–voltage characteristics and dynamic correlation of rotating vortex-lattice rings

We report the unusual dc current–voltage (I–V) characteristics for the vortex-lattice rings rotated by a dc current I superimposed with ac currents of different amplitudes Irf in a Corbino disk of an amorphous MoxGe1−x film. As Irf is increased from zero, the I–V curve in the large I region shows a trend to decrease. This is in contrast to the usual behavior of vortex flow in which ac-induced depinning leads to an increase in the flow voltage. We attribute the finding to the Irf-induced growth in the transverse dynamic correlation of the rotating lattice rings.