New aspects of microwave properties of Nb in the mixed state

Abstract

We present a study of the frequency dependence of the vortex dynamics in a conventional superconductor. We have employed a swept-frequency, Corbino-disk technique to investigate the temperature (3.6K-Tc) and high-field (from Hc2/2 to Hc2) microwave complex resistivity in Nb thin (20-40 nm) films as a function of the frequency (1-20 GHz). We have found several previously unnoticed features: (i) a field-dependent depinning frequency in the GHz range; (ii) deviations from the accepted frequency dependence, that can be ascribed to some kind of vortex creep; (iii) the presence of switching phenomena, reminiscent of vortex instabilities. We discuss the possible origin of the features here reported.

5 pages, 3 figures, presented at VORTEX VI Conference, to appear on Physica C

References in corpus (4)

• Coupling of two superconductors through a ferromagnet : evidence for a pi-junction
• Reliable determination of vortex parameters from measurements of the microwave complex resistivity
• Unconventional Vortex Dynamics in Mesoscopic Superconducting Corbino Disks
• Measurements of surface impedance of superconductors as a function of frequency in microwave range

Cited by in corpus (11)

• Microwave spectroscopy on heavy-fermion systems: probing the dynamics of charges and magnetic moments
• Surface-resistance measurements using superconducting stripline resonators
• Wideband microwave measurements in Nb/Pd${}_{84}$Ni${}_{16}$/Nb structures and comparison with thin Nb films
• Vortex ratchet reversal in an asymmetric washboard pinning potential subject to combined dc and ac stimuli
• Vortex motion in Nb/PdNi/Nb trilayers: new aspects in the flux flow state
• Microwave study of superconducting Sn films above and below percolation
• Microwave properties of Nb/PdNi/Nb trilayers. Observation of flux flow in excess of Bardeen-Stephen theory
• ${}^4$He sample probe for combined microwave and dc transport measurements
• Niobium stripline resonators for microwave studies on superconductors
• Role of non-linear effects and standing waves in microwave spectroscopy: Corbino measurements on superconductors and VO${}_2$
• Microwave probing of bulk dielectrics using superconducting coplanar resonators in distant-flip-chip geometry