Superconductivity in monolayer Pb on Si(111) from first principles

Observation of superconductivity in a single layer of Pb on the (111) surface of bulk silicon has renewed interest in a longstanding question; can superconductivity persist to the ultimate atomic limit? Using first-principles techniques, we investigate the total electron–phonon coupling in monolayer Pb supported by a Si(111) substrate. Our ultra-fine sampling of the electronic structure, lattice dynamics and electron–phonon matrix elements in the nearly two-dimensional Brillouin zone yields a total electron–phonon coupling parameter which explains the experimentally observed superconducting transition temperature of 1.83 K [T. Zhang, et al., Nat. Phys. 6 (2010) 104]. The observed suppression of the superconducting transition temperature from the bulk value of 7.2 K is found to arise from the interplay of reduced electron–phonon matrix elements and a modification of the lattice dynamics resulting from the Pb–Si bonding.