Enhanced superconductivity in Al nanofilms grown by molecular beam epitaxy

Pin-Chi Liao^1*, Ching-Chen Yeh¹, Yen-Ting Fan¹, Sheng-Di Lin¹, Chi-Te Liang¹

¹物理系, 國立台灣大學, 台北市, Taiwan

* Presenter:Pin-Chi Liao, email:g20412005.ep04@g2.nctu.edu.tw

Al is one of the most widely studied single-element superconductors. Pioneering work on the enhanced Tc (compared to that of bulk Al (1.2 K)) in Al-based systems was mostly done on thin films that are polycrystalline, granular or mixed with Ge or Al₂O₃. Such enhanced superconductivity in Al nanofilms seemed to be in contrast to the seminal work in which the Tc decreases with increasing film thickness6.
In order to obtain a better understanding of how Tc varies with changing the thin film thickness, here, we perform a thorough study of MBE-grown Al nanofilms of different thicknesses. Our results suggest that the strain effect from different substrates and increased electron-phonon coupling play an essential role in the enhanced superconductivity in MBE-grown Al nanofilms. In contrast, the effect of disorder-related suppression on the Tc, as clearly demonstrated previously, is not significant in our high-quality MBE-grown Al nanofilms.

Keywords: Superconductivity, Topological transition, Aluminum nanofilms