Double peaks in the dissipation of vibrating superconductors

The two distinct peaks observed as a function of temperature in the dissipation of vibrating superconducting slabs in a tilted magnetic field are explained by thermally activated flux diffusion across the thickness and width (or length) of the slab. These conspicuous peaks thus do not necessarily indicate multiple phase transitions of the flux-line lattice as proposed previously. Anisotropic mobility of the flux lines may increase or decrease the separation of the peaks.