Evidence of surface superconductivity and multi-quanta vortex states in a weakly-pinned single crystal of Ca3Ir4Sn13

Abstract We report here the observation of anomalous paramagnetic signal(s) in the isofield field-cooled cool-down magnetization scans ( M FCC ( T ) ) recorded for a single crystal of a low T c superconductor Ca 3 Ir 4 Sn 13 . Novel features emanating from the M FCC ( T ) response include an oscillatory magnetization behavior below T c and a rich multiplicity (non-uniqueness) in magnetization ranging from diamagnetism to paramagnetism at a given H , T value. The metastability in M FCC ( T ) has been ascribed to non-unique coexistence of multi-quanta vortex states ( L Φ 0 , Φ 0 = hc / 2 e , L > 1 ) and single quantum ( L = 1 , Abrikosov) vortices. Additionally, the isothermal M ( H ) scans recorded across a short window of temperature just below T c show evidence for only the multi-quanta vortex states in the domain of surface superconductivity, with no fingerprint(s) of pinned Abrikosov lattice.