Electronic and superconducting properties of CoSi2 films on silicon — An unconventional superconductor with technological potential

Abstract

We report the observation of unusual normal-state electronic conduction properties and superconducting characteristics of high-quality CoSi${}_2$/Si films grown on silicon Si(100) and Si(111) substrates. A good understanding of these features shall help to address the underlying physics of the unconventional pairing symmetry recently discovered in transparent CoSi${}_2$/TiSi${}_2$ heterojunctions (Chiu et al., 2021; Chiu et al., 2023), where CoSi${}_2$/Si is a superconductor with a superconducting transition temperature $T_c\simeq$ (1.1–1.5) K, dependent on its dimensions, and TiSi${}_2$ is a normal metal. In CoSi${}_2$/Si films, we find a pronounced positive magnetoresistance caused by the weak-antilocalization effect, indicating a strong Rashba spin–orbit coupling (SOC). This SOC generates two-component superconductivity in CoSi${}_2$/TiSi${}_2$ heterojunctions. The CoSi${}_2$/Si films are stable under ambient conditions and have ultralow 1/$f$ noise. Moreover, they can be patterned via the standard lithography techniques, which might be of considerable practical value for future scalable superconducting and quantum device fabrication.