Unusual vortex dynamics in the Meissner phase in the Corbino disk

We have studied vortex dynamics induced by dc current <f>I</f> in the Meissner phase of a thick amorphous MoxSi1-x film with the strip-like and Corbino-disk (CD) contact geometries. We have measured the time evolution of voltage <f>V(t)</f> induced by <f>I</f>. It is found that only in the CD unusual large voltage pulses appear almost periodically with a period of typically 40 s and with the pulse width of about 5 s. Both times are much longer than the characteristic time for free vortices to rotate (half) in the circles, indicating that the observed voltage pulses originate from collective motion of many vortices which leads to large density fluctuations of moving vortices. [Copyright &y& Elsevier]