Ab Initio Study of the Electron–Phonon Coupling in Ultrathin Al Layers

The impact of film thickness to the electron–phonon coupling and the critical temperature of the superconducting transition, as well as to the structural, phonon and electronic properties of Al films in the ultrathin regime, was studied by means of ab initio calculations. The presence of the inevitable quantum fluctuations in the regime of 5 to 9 atomic layers was found not to be detrimental for the transition critical temperature, as quantum confinement was found to have a monotonically positive impact. As calculations were performed on perfect crystalline films, results of this work give further indirect evidence of the impact of the experimentally observed defects on the superconducting transition. The reduction of the dimensions of materials in the critically low regime of quantum effects can unlock new prospects for high Tc superconducting devices, such as cryogenic light detectors and superconducting single-electron transistors; hence, the understanding of the underlying mechanisms is required for the deterministic tailoring of their properties.