Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
CIC nanoGUNE and Ikerbasque, Basque Foundation for Science, Tolosa Hiribidea 78, Donostia-San Sebastian 20018, Spain.
Phys Rev Lett. 2015 Apr 17;114(15):157001. doi: 10.1103/PhysRevLett.114.157001. Epub 2015 Apr 14.
The type I superconductor lead (Pb) has been theoretically predicted to be a two-band superconductor. We use scanning tunneling spectroscopy (STS) to resolve two superconducting gaps with an energy difference of 150 μeV. Tunneling into Pb(111), Pb(110), and Pb(100) crystals reveals a strong dependence of the two coherence peak intensities on the crystal orientation. We show that this is the result of a selective tunneling into the two bands at the energy of the two coherence peaks. This is further sustained by the observation of signatures of the Fermi sheets in differential conductance maps around subsurface defects. A modification of the density of states of the two bands by adatoms on the surface confirms the different orbital character of each of the two subbands.
I 型超导体铅（Pb）在理论上被预测为一个双带超导体。我们使用扫描隧道谱（STS）来分辨两个超导能隙，其能量差为 150 μeV。隧穿到 Pb(111)、Pb(110) 和 Pb(100) 晶体揭示了两个相干峰强度对晶体取向的强烈依赖关系。我们表明，这是由于在两个相干峰的能量处选择性地隧穿到两个能带的结果。在亚表面缺陷周围的微分电导图中观察到费米面的特征，进一步证实了这一点。表面上的 adatoms 对两个能带的态密度的修饰证实了两个子带的每个轨道特性的不同。
