Magnetic-field dependence of Fiske resonances in Nb/p-type InAs/Nb weak links

We present measurements of the temperature and magnetic-field dependence of the critical current Ic in Nb/InAs/Nb weak links. We also report on the magnetic-field dependence of resonances in the current-voltage (I-V) characteristics, the so-called Fiske resonances. Their magnetic-field dependence can be explained by a simplified resistively shunted junction (RSJ) model. We also measure a Fiske resonance with a period half as large as the period of the corresponding Fraunhofer pattern. This cannot be understood within the simplified RSJ model. It may be related to deviations From the sinusoidal phase dependence of the critical current in this type of weak link. (C) 1998 Elsevier Science Ltd. All rights reserved.