Chiral spin texture in the charge-density-wave phase of the correlated metallic Pb/Si(111) monolayer

TL;DR

This study combines experimental and theoretical methods to reveal chiral spin textures and strong spin-orbit effects in the charge-density-wave phases of Pb/Si(111), highlighting complex electronic interactions and spin polarization phenomena.

Contribution

It provides the first detailed analysis of spin textures and relativistic effects in the charge-density-wave phases of Pb/Si(111) monolayers, integrating STS experiments with first-principles calculations.

Findings

Spin-orbit interaction causes significant energy splitting in both phases.

Correlated low-temperature phase features Hubbard bands and $3\times3$ periodicity.

Fermi surface analysis shows in-plane spin polarizations with opposite helicities.

Abstract

We investigate the 1/3 monolayer $\alpha$-Pb/Si(111) surface by scanning tunneling spectroscopy (STS) and fully relativistic first-principles calculations. We study both the high-temperature $\sqrt{3}\times\sqrt{3}$ and low-temperature $3\times 3$ reconstructions and show that, in both phases, the spin-orbit interaction leads to an energy splitting as large as $25\%$ of the valence-band bandwidth. Relativistic effects, electronic correlations and Pb-substrate interaction cooperate to stabilize a correlated low-temperature paramagnetic phase with well-developed lower and upper Hubbard bands coexisting with $3\times3$ periodicity. By comparing the Fourier transform of STS conductance maps at the Fermi level with calculated quasiparticle interference from non-magnetic impurities, we demonstrate the occurrence of two large hexagonal Fermi sheets with in-plane spin polarizations and opposite helicities.