Dynamics of Driven Vortex Lattice Probed by Microwave Technique

H. Kurokawa, F. Nabeshima and A. Maeda
Dept. of Basic Sci., Univ. Tokyo
Dynamics of driven vortex lattice in superconductor has attracted attention as a driven disordered system to study various nonequilibrium phenomena such as disordered flow and nonequilibrium phase transition. These phenomena come from the pinning force originated from disorder. So far, I-V measurements are widely used to investigate nonequilibrium properties of the driven vortices. In addition, other technique, such as velocity noise[1] and small angle neutron scattering[2] were performed to study the driven vortex lattice. However, microscopic nature of pinning force, particularly that for moving vortices, is still poorly understood experimentally. In other words, how driven vortices responses to time-dependent force has not been revealed yet. In order to obtain further insight, we measure ac response of vortex lattice under dc driving force. We fabricated 8 GHz transmission line resonators made of Nb and succeeded in capturing the changes w and without dc driving force. These changes show hysteresis as a function of dc driving force. We will discuss how these change as a function of frequency also.
[1] A. Maeda et al., Phys. Rev. B 65, (2002) 054506.
[2] U.Yaron et al., Nature 376, (1995) 753.