Doping-dependent charge- and spin-density wave orderings in a monolayer of Pb adatoms on Si(111)

TL;DR

This study explores how doping influences charge and spin density wave orders in a Pb adatom monolayer on Si(111), revealing complex phase behavior driven by electronic interactions and structural effects.

Contribution

It provides a comprehensive phase diagram considering Coulomb interactions, spin-orbit coupling, and structural transitions, highlighting coexistence and doping-dependent textures.

Findings

Charge and spin density waves coexist in certain doping regimes.

Doping levels significantly alter the geometry of density wave textures.

The phase diagram explains experimental observations of chiral spin textures.

Abstract

In this work we computed the phase diagram as a function of temperature and doping for a system of lead adatoms allocated periodically on a silicon (111) surface. This Si(111):Pb material is characterized by a strong and long-ranged Coulomb interaction, a relatively large value of the spin-orbit coupling, and a structural phase transition that occurs at low temperature. In order to describe the collective electronic behavior in the system, we perform many-body calculations consistently taking all these important features into account. We find that charge- and spin-density wave orderings coexist with each other in several regions of the phase diagram. This result is in agreement with the recent experimental observation of a chiral spin texture in the charge density wave phase in this material. We also find that geometries of the charge and spin textures strongly depend on the doping level. The formation of such a rich phase diagram in the Si(111):Pb material can be explained by a combined effect of the lattice distortion and electronic correlations.