A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)2

K. Hashimoto, K. Cho, T. Shibauchi*, S. Kasahara, Y. Mizukami, R. Katsumata, Y. Tsuruhara, T. Terashima, H. Ikeda, M. A. Tanatar, H. Kitano, N. Salovich, R. W. Giannetta, P. Walmsley, A. Carrington, R. Prozorov, Y. Matsuda

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

258 Citations (Scopus)


In a superconductor, the ratio of the carrier density, n, to its effective mass, m*, is a fundamental property directly reflecting the length scale of the superfluid flow, the London penetration depth, lambda(L). In two-dimensional systems, this ratio n/m* (similar to 1/lambda(2)(L)) determines the effective Fermi temperature, T-F. We report a sharp peak in the x-dependence of lambda(L) at zero temperature in clean samples of BaFe2(As1-xPx)(2) at the optimum composition x = 0.30, where the superconducting transition temperature T-c reaches a maximum of 30 kelvin. This structure may arise from quantum fluctuations associated with a quantum critical point. The ratio of T-c/T-F at x = 0.30 is enhanced, implying a possible crossover toward the Bose-Einstein condensate limit driven by quantum criticality.

Original languageEnglish
Pages (from-to)1554-1557
Number of pages4
Issue number6088
Publication statusPublished - 22 Jun 2012


  • HIGH-T-C
  • BCS


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