Electronic structure, spin-orbit interaction and electron-phonon coupling of triangular adatom lattices on semiconductor substrates

Abstract

A one-third monolayer of the heavy metals Sn and Pb deposited on semiconductor substrates can lead to a $\sqrt{3}\times \sqrt{3}$ surface reconstruction, constituting an exciting triangular lattice material platform. A long history of experiments identified charge-ordered and magnetic ground states. These discoveries were accompanied by a decades-long debate of whether electron correlations or other effects involving phonons are the driving force of the symmetry-broken states. The most recent discovery of superconductivity in boron-doped Sn/Si(111) with a $T_c$ between 5K and 9K led to a renewed excitement. Here we revisit the electronic and phononic properties of Sn and Pb adatom triangular lattices on Si(111) and SiC(0001). For all materials we compute relativistic bandstructures using DFT+$U$ where $U$ is only applied to the substrate atoms in order to adjust the band gap to match the experimental value; as a consequence, some of the resulting tight-binding parameters of the metallic surface band differ substantially compared to previous studies. Remarkably, for Pb/SiC(0001) we predict Rashba spin-orbit coupling as large as 45% of the nearest-neighbor hopping energy. In addition, we compute the phonon spectra and electron-phonon coupling constants for all materials, and for Pb/Si(111) even relativistically although the inclusion of spin-orbit coupling has surprisingly little effect on the electron-phonon coupling constant. We conclude that the resulting couplings are too weak to account for electron-phonon mediated superconductivity in any of these materials.

15 pages, 9 figures, 9 tables; v2: as published [now also including results for Sn/Ge(111) and Pb(Ge(111)]

References in corpus (21)

• Climbing the Density Functional Ladder: Non-Empirical Meta-Generalized Gradient Approximation Designed for Molecules and Solids
• Wannier90 as a community code: new features and applications
• Implementation strategies in phonopy and phono3py
• Long-range Coulomb interactions in surface systems: a first principles description within self-consistently combined GW and dynamical mean field theory
• Triangular Mott-Hubbard Insulator Phases of Sn/Si(111) and Sn/Ge(111) Surfaces
• Realization of a hole-doped Mott insulator on a triangular silicon lattice
• Evidence for chiral superconductivity on a silicon surface
• Superconductivity in a hole-doped Mott-insulating triangular adatom layer on a silicon surface
• Triplet Superconductivity from Nonlocal Coulomb Repulsion in an Atomic Sn Layer Deposited onto a Si(111) Substrate
• Triangular Spin-Orbit-Coupled Lattice with Strong Coulomb Correlations: Sn Atoms on a SiC(0001) Substrate
• Realistic modeling of the electronic structure and the effect of correlations for Sn/Si(111) and Sn/Ge(111) surfaces
• Chiral spin texture in the charge-density-wave phase of the correlated metallic Pb/Si(111) monolayer
• Spin-orbit coupling and magnetic interactions in Si(111):{C,Si,Sn,Pb}
• Chiral d-wave Superconductivity in a Triangular Surface Lattice Mediated by Long-range Interaction
• Correlation-driven charge order in a frustrated two-dimensional atom lattice
• Zero-bias anomaly in nano-scale hole-doped Mott insulators on a triangular silicon surface
• Nanoskyrmion engineering with $sp$-electron materials: Sn monolayer on SiC(0001) surface
• Charge density wave in single-layer Pb/Ge(111) driven by Pb-substrate exchange interaction
• Experimental observation of pseudogap in a modulation-doped Mott insulator: Sn/Si(111)-($\sqrt{3}\times \sqrt{3}$)-R30${}^{\text{o}}$
• Phonon-induced electronic relaxation in a strongly correlated system: the Sn/Si(111) $(\sqrt{3}\times \sqrt{3})$ adlayer revisited
• Chern number landscape of spin-orbit coupled chiral superconductors

Cited by in corpus (1)

• The electronic structure of a doped Mott-Hubbard surface