Spin-flip Scattering at a Chiral Interface of Helical Chains (2501.08611v4)

Abstract: We investigate spin-flip scattering processes of electrons when they pass a chiral interface, which is the boundary between right- and left-handed one-dimensional chain. We construct a minimal $p$-orbital model consisting of the right- and left-handed one-dimensional threefold helical chains connected at $z=0$ with the nearest neighbor hopping and the spin-orbit coupling. The dynamics of spin-polarized wave packet passing through the interface, the Green's functions, and electronic states near the interface are analyzed numerically. We find that the microscopic structure of the interface is important and this strongly affects the local electronic orbital state. This in addition to the spin-orbit coupling determines whether the spin flip occurs or not at the chiral interface and suggests a possible spin transport control by the orbital configuration at the chiral interface.

• The paper demonstrates how spin-flip scattering at chiral interfaces relies on the presence or absence of localized orbital states, with notable effects observed at different geometrical configurations.
• It employs a p‐orbital tight-binding model and numerical simulations to compare spin behavior at φ=0, where spin flips occur, and φ=2π/3, where they are suppressed.
• These findings offer actionable insights for designing spintronic devices by controlling spin polarization through engineered chiral interfaces in advanced materials.

Analysis of Spin-Flip Scattering at Chiral Interfaces of Helical Chains

The paper presented by Matsubara and Hattori explores the complex phenomena associated with electron spin-flip scattering at chiral interfaces, specifically at the junctions of right-handed (RH) and left-handed (LH) one-dimensional helical chains. The authors employ a dedicated $p$-orbital tight-binding model to capture the underlying physics influenced by spin-orbit coupling (SOC) within these unique chiral systems. By employing numerical simulations, the paper elucidates the dependencies of spin transport on the local electronic states and chirality of the interfacing domains.

Key Observations and Numerical Analysis

Chiral crystals, defined by the absence of mirror and inversion symmetries, possess distinct right-handed and left-handed configurations. Understanding spin-dependent transport phenomena, such as spin-flip scattering, is crucial due to potential applications in spintronic devices and information processing technologies. In this paper, the chiral interface (CIF), where RH and LH chains meet, serves as a focal point for analyzing spin dynamics.

The numerical analysis conducted in this research reveals two primary scenarios based on the structural parameter $\phi$, which influences the interface's geometry. For $\phi=0$, spin flips are observed when electrons cross the CIF. This scenario aligns with results indicating no localized electronic modes at the interface, allowing transitions through SOC. Contrastingly, for $\phi=2\pi/3$, localized modes at the interface impede orbital transitions necessary for spin flips, resulting in no spin-flip scattering. These results emphasize that the presence of localized orbital states near the CIF critically affects electron spin behavior.

Implications and Theoretical Contributions

The findings have several significant implications. Practically, they suggest mechanisms for controlling spin polarization and transport properties in chiral materials by tailoring localized electronic structures at interfaces. Understanding how the orbital character and its coupling to spins govern transport phenomena offers pathways for designing novel materials with specific electronic and magnetic properties.

Theoretically, this work contributes to spin-transport physics by demonstrating how chiral interfaces can both facilitate and obstruct spin flips, providing a deeper understanding of the interplay between structural chirality and SOC. The paper highlights the importance of local orbital configurations in determining macroscopic spin-transport properties, opening avenues for further exploration of multipolar and non-coplanar interfacing in chiral materials.

Future Directions

Future research directions could include exploring additional parameters influencing CIF characteristics beyond the simplistic $\phi$ modulation, such as introducing intermediate atomic layers or investigating non-linear SOC effects. Additionally, experimental verification of the described spin transport mechanisms in actual chiral materials will be critical. Extending this analysis to multi-dimensional systems or alternative chiral structures could yield richer insights into spintronic applications.

In conclusion, Matsubara and Hattori's work exemplifies a meticulous investigation into chiral interface physics, advancing both theoretical comprehension and practical considerations for spin-based technologies. The nuanced exploration of electron dynamics underscores the subtle yet pivotal role of atomic and electronic structure in designing future materials and devices that leverage the intricate balance of spin, orbit, and chirality.