Nanoarchitecture: Toward Quantum‐Size Tuning of Superconductivity

Quantum confinement is known to affect a nanosized superconductor through quantum‐size variations of the electronic density of states. Here, it is demonstrate that there is another quantum‐confinement mechanism overlooked in previous studies. In particular, it is found that the electron–electron attraction can be enhanced due to quantum‐confinement modifications of electronic wave functions. The superconducting correlations are strengthened by such quantum mechanical effect, which creates a subtle interplay with surface–substrate phonon modifications. The combined effect depends on nanofilm thickness and can be controlled by nanoarchitechture. The calculations are in a reasonable agreement with experiments performed on high‐quality aluminum films. These findings shed light on the long‐standing problem of the size dependence of the critical temperature in low‐dimensional superconductors.