Use the superconducting proximity effect to investigate alkali metal films and the comparison between the experiment and theory

Unrestricted Bilayers of Pb and the alkali metals Cs, Rb, K and Na were quench condensed on the quartz plate. The transition temperature measurement provides information about interface barriers between the Pb and the alkali metals. Such a barrier, which is not due to impurities or oxidation, is particularly large in Pb/Cs sandwiches.; The thin K film is forced into an insulating state by being covered with sub-mono-layers of Pb. The SPE is used to investigate the electronic change in the alkali film. The K film behaves as if itselectrons are unable to carry a current in the x-y-plane but can easily move in the z-direction. This shows on the length scale of the K film thickness, the electronic properties of the film do notchange noticeably during the metal-insulator transition.; The superconducting proximity effect is investigated for SN-double layers in the thin film limit. In this regime, the normalized initial slope S{sn}=(d{s}/T{s})|dT{c}/dd{n}| is independent of the thickness of the superconductor, the mean free path of the films and the transparency of the interface if it is not too small. The transition temperature T{c} is compared with a numerical calculation developed in our group. The deviation between the experiment and theory decreases from the normal metal to the superconductor with a relative high transition temperature. The deviation factor decreases from 2.5 for Cu, Ag, Au, Mg to 1.5 forCd, Zn, Al and finally no disagreement for In and Sn.; A weak perpendicular magnetic field is applied on the super- and normal conductor double layers. The difference of the transition temperature dT{c} measured with and without magnetic field increases with increasing the normal metal thickness. A quantitative explanation is given based on the increased dephasing of the electrons in the magnetic field. Numerical calculation of the transition temperature based on the strong coupling theory is also given and compared with the experimental results.