量子尺寸效应导致的铅薄膜材料的奇异超导性质

Superconductivity modulated by quantum size effects

我们在硅衬底上制备出厚度在原子尺度上可控、宏观尺度上均匀的铅薄膜。观察到随着厚度一个原子层一个原子层增加时薄膜超导转变温度的振荡现象。我们证明,这种振荡行为是量子尺寸效应的结果。在这种薄膜中,电子德布罗意波的干涉行为类同于光的法布里 玻罗干涉,会导致量子阱态的形成。量子阱态的形成改变了费米能级附近的电子态密度和电声子耦合强度,从而最后导致了超导转变温度的变化。研究结果表明:通过精确控制这种厚度敏感的量子尺寸效应,可以调制材料的物理和化学性质。

We show that by precise control of film growth in the ultimate atomic scale, one is able to grow atomically flat Pb films on Si substrate with an exact uniform thickness over macroscopic scales, and that the superconducting transition temperature (Tc) of such films exhibits an oscillatory behavior as the film thickness is increased by one atomic layer at a time. We demonstrate that this non-monotonic dependence is a spectacular manifestation of the Fabry-Perot modes of electron standing waves in the ultrathin films, known as quantum well states, which modulate the electron density of states near the Fermi level and electron-phonon coupling-the two factors controlling superconductivity transition. Our work has thus opened the door for quantum engineering of superconductivity and other properties of thin films.