Emergence of superconductivity in a Dirac nodal-line Cu2Si monolayer: ab initio calculations

Abstract

Following the prediction given by first-principles simulations [J. Am. Chem. Soc.137, 2757 (2015)], a Dirac nodal-line Cu₂Si monolayer has been successfully synthesized on a Cu(111) surface [Nat. Commun.8, 1007 (2017)] or on a Si(111) substrate [Phys. Rev. Mater.3, 044004 (2019)]. However, its superconducting properties have never been reported in experiments or theory. Here, through first-principles calculations, we study its electron and phonon properties and electron–phonon coupling to investigate the possibility of superconductivity for a metallic Cu₂Si monolayer. The results show that it is an intrinsic BCS-type superconductor, with the estimated superconducting temperature T_c being ∼4.1 K. We further find that the Fermi surface nesting is partially responsible for its superconducting character. Carrier doping as well as biaxial strains will suppress the T_c. Our results help to explain the challenges to experimentally probe superconductivity in substrate-supported Cu₂Si monolayers and provide clues for further experiments.