科研之友
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摘要
The thickness dependence of the superconducting energy gap Delta(La) of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature T-c as a function of the inverse film thickness. For the thick, bulk-like films, Delta(La) and T-c are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large T-c originates in the superior purity of the samples investigated here.
- 出版日期2014-10-22
