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arXiv · cond-mat/9811187

Lower critical field H_c1 and barriers for vortex entry in Bi_2Sr_2CaCu_2O_{8+delta} crystals

M. Nideroest·R. Frassanito·M. Saalfrank·A. C. Mota·G. Blatter·V. N. Zavaritsky·T. W. Li·P. H. Kes
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Abstract

The penetration field H_p of Bi_2Sr_2CaCu_2O_{8+delta} crystals is determined from magnetization curves for different field sweep rates dH/dt and temperatures. The obtained results are consistent with theoretical reports in the literature about vortex creep over surface and geometrical barriers. The frequently observed low-temperature upturn of H_p is shown to be related to metastable configurations due to barriers for vortex entry. Data of the true lower critical field H_c1 are presented. The low-temperature dependence of H_c1 is consistent with a superconducting state with nodes in the gap function. [PACS numbers: 74.25.Bt, 74.60.Ec, 74.60.Ge, 74.72.Hs]

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M. Nideroest, R. Frassanito, M. Saalfrank, A. C. Mota, G. Blatter, V. N. Zavaritsky, T. W. Li, P. H. Kes. 1998-11-13. Lower critical field H_c1 and barriers for vortex entry in Bi_2Sr_2CaCu_2O_{8+delta} crystals. https://doi.org/10.1103/physrevlett.81.3231

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