Observation of correlated spin-orbit order in a strongly anisotropic quantum wire system

TL;DR

This study observes a novel spin-orbit density wave in Pb-atomic wires on Si(557), revealing how electronic interactions influence spin textures and symmetry breaking in quantum wire systems.

Contribution

It reports the first experimental observation of an exotic spin-orbit density wave in a strongly anisotropic quantum wire system, linking Coulomb interactions to spin-orbit entanglement.

Findings

Spin polarization and coherence length decrease with reduced Coulomb interactions.

Spontaneous spin-rotation symmetry breaking observed without breaking time-reversal symmetry.

Spin-momentum structure modulation depends on excess coverage.

Abstract

Quantum wires with spin-orbit coupling provide a unique opportunity to simultaneously control the coupling strength and the screened Coulomb interactions where new exotic phases of matter can be explored. Here we report on the observation of an exotic spin-orbit density wave in Pb-atomic wires on Si(557) surfaces by mapping out the evolution of the modulated spin-texture at various conditions with spin- and angle-resolved photoelectron spectroscopy. The results are independently quantified by surface transport measurements. The spin polarization, coherence length, spin dephasing rate, and the associated quasiparticle gap decrease simultaneously as the screened Coulomb interaction decreases with increasing excess coverage, providing a new mechanism for generating and manipulating a spin-orbit entanglement effect via electronic interaction. Despite clear evidence of spontaneous spin-rotation symmetry breaking and modulation of spin-momentum structure as a function of excess coverage, the average spin-polarization over the Brillouin zone vanishes, indicating that time-reversal symmetry is intact as theoretically predicted.