Giant chirality-induced spin polarization in twisted transition metal dichalcogenides

TL;DR

This paper demonstrates that twisted transition metal dichalcogenides exhibit a giant chirality-induced spin polarization, exceeding 50%, due to structural chirality and spin-orbit coupling, opening new avenues for spin control in quantum materials.

Contribution

It reveals that atomically-thin chiral crystals, specifically twisted TMDCs, can produce large spin polarization effects driven by chirality and spin-orbit interactions, a novel insight in condensed matter physics.

Findings

Spin polarization exceeds 50% in twisted MoTe2.

Chirality and spin-orbit coupling are key to large CISS effects.

Twisted quantum materials serve as tunable platforms for spin control.

Abstract

Chirality-induced spin selectivity (CISS) is an effect that has recently attracted a great deal of attention in chiral chemistry and that remains to be understood. In the CISS effect, electrons passing through chiral molecules acquire a large degree of spin polarization. In this work we study the case of atomically-thin chiral crystals created by van der Waals assembly. We show that this effect can be spectacularly large in systems containing just two monolayers, provided they are spin-orbit coupled. Its origin stems from the combined effects of structural chirality and spin-flipping spin-orbit coupling. We present detailed calculations for twisted homobilayer transition metal dichalcogenides, showing that the chirality-induced spin polarization can be giant, e.g. easily exceeding $50\%$ for ${\rm MoTe}_2$. Our results clearly indicate that twisted quantum materials can operate as a fully tunable platform for the study and control of the CISS effect in condensed matter physics and chiral chemistry.