Alternating-chiral charge density waves and associated spin polarization in monolayered NbTe₂.

Abstract

Intertwining of different quantum degrees of freedom manifests exotic quantum phenomena in many-body systems, especially in reduced dimensionality. Here we show that monolayered NbTe₂ serves as a promising platform where lattice, charge, and spin degrees of freedom manifest cooperatively, leading to a threading order of chirality. Through meticulous real-space atomic structure analysis, we reveal that the √19 × √19 phase of NbTe₂ encodes alternating-chiral atomic displacements alongside charge density order, characterized by two chiral units of opposite handedness within the reconstructed cell. Using spin-polarized scanning tunneling microscopy, complemented by correlative techniques, we present evidence for emergent spin polarizations spreading over the primitive cell, where the spin texture appears to be correlated with the alternating handedness of chiral order. Our first-principles studies identify the origin of intertwined orders as being correlation-driven, with the threading order of chirality emerging when the on-site Coulomb repulsion exceeds a critical value. The observed spin arrangement can be understood in terms of a hybrid character, combining contributions from itinerant electrons and localized d-orbitals. Collectively, these findings expand the realm of chiral order in correlated electron systems and facilitate an appealing platform for chiral spintronic and related applications.