[1Dp01-09] Surface Science(SS1) Physical Property

[1Dp02] Superconductivity of Ca-intercalated bilayer graphene enhanced by confinement epitaxy

*Satoru Ichinokura¹, Kei Tokuda¹, Masayuki Toyoda¹, Kiyohisa Tanaka², Susumu Saito¹, Toru Hirahara¹ (1. Department of Physics, Tokyo Institute of Technology, 2. UVSOR Facility, Institute for Molecular Science)

We have identified a layer of metallic calcium cultivated at the interface between the superconducting bilayer graphene intercalated with calcium and the SiC substrate, providing substantiation for the emergence of confinement epitaxy. By employing an ultrahigh-vacuum multi-probe system encompassing photoemission spectroscopy and transport measurements, we have examined the interplay between the electronic states engendered by the Ca-sublayer and superconductivity. The free-electron-like band derived from the sublayer hybridized with a Dirac band culminating in the genesis of a flat band. Correspondingly, we have observed an elevation in the critical temperature for superconductivity. The enhancement of superconductivity is regulated by the intensified many-body interaction arising from the presence of the flat band or the amelioration of substrate-induced scattering phenomena due to the interfacial metallic layer. We postulate that this hitherto undisclosed confinement epitaxy acts as an underlying factor contributing to the variability of the critical temperature, a long-standing unresolved matter within this system.