Momentum-Space Spin Antivortex and Spin Transport in Monolayer Pb

TL;DR

This paper discovers a topologically stable spin anti-vortex in monolayer Pb, revealing its impact on spin transport phenomena and Fermi surface topology, with potential applications in spintronics.

Contribution

It identifies a novel, topologically stable spin anti-vortex in monolayer Pb and explores its effects on spin transport and Fermi surface transitions.

Findings

Presence of a topologically stable spin anti-vortex at specific momenta.

Fermi surface Lifshitz transition associated with the anti-vortex.

Rapid variation in spin response coefficients near the anti-vortex energy.

Abstract

Non-trivial momentum-space spin texture of electrons can be induced by spin-orbit coupling and underpins various spin transport phenomena, such as current-induced spin polarization and spin Hall effect. In this work, we find a non-trivial spin texture, spin anti-vortex, can appear at certain momenta on the $\Gamma-\text K$ line in 2D monolayer Pb on top of SiC. Different from spin vortex due to the band degeneracy in the Rashba model, the existence of this spin anti-vortex is guaranteed by Poincare-Hopf theorem and thus topologically stable. Accompanied with this spin anti-vortex, a Lifshtiz transition of Fermi surfaces occur at certain momenta on the $\text K- \text M$ line, and both phenomena are originated from the anti-crossing between the $j=1/2$ and $j=3/2$ bands. A rapid variation of the response coefficients for both the current-induced spin polarization and spin Hall conductivity is found when the Fermi energy is tuned around the spin anti-vortex. Our work demonstrates the monolayer Pb as a potentially appealing platform for spintronic applications.