Wednesday, February 3, 2010, 10:30 am — Bldg. 703, Large Conference Room
I will present the measurements of the superconducting energy gap of epitaxially grown Pb films as a function of the layer thickness. Ultrathin Pb films (5 – 18 ML) on Si(111) were grown by low temperature deposition followed by room temperature annealing. A home-built, low-temperature scanning tunneling microscope (STM) was used to probe the relevant electronic and geometric properties. The layer-dependent energy gap and transition temperature (Tc) show persistent quantum oscillations down to the lowest thickness without any sign of suppression. Moreover, by comparison with the quantum-well states measured above Tc and the theoretical calculations, we found that the Tc oscillation correlates directly with the density of states oscillation at the Fermi level (EF). The oscillation is manifested by the phase matching of the Fermi wavelength and the layer thickness, resulting in a bilayer periodicity modulated by a longer wavelength quantum beat.
Hosted by: Evgueni Nazaretski
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