Large energy dissipation due to vortex dynamics in mesoscopic Al disks

We present systematic resistance measurements of mesoscopic Al disk samples with three different sizes and compare them with those of an Al-wire sample. When a magnetic field is applied perpendicular to the disks, a large excess resistance, which is approximately six times larger than the normal-state resistance (Rn), appears near the critical field of the Al leads connected to the disks. In the low-field region of the large excess resistance, successive resistant peaks are observed. These peaks are ascribed to the transitions of the vortex states in the disk. Remarkably, some of the resistance peaks are significantly larger than Rn, indicating that the Al disks are superconducting in the excess resistance state. Such behavior has never been observed in the case of a wire sample. These results suggest that the vortices in the mesoscopic disks cause anomalously large energy dissipation when they are driven by the sample current. The superconducting current leads connected to the disks also play a crucial role in the occurrence of the large excess resistance.