Real-space observation of incommensurate spin density wave and coexisting charge density wave on Cr (001) surface.

Hu, Yining; Zhang, Tianzhen; Zhao, Dongming; Chen, Chen; Ding, Shuyue; Yang, Wentao; Wang, Xu; Li, Chihao et al. · Nat Commun · 2022

basic_science · Level V

Where this comes from

Abstract

In itinerant magnetic systems, a spin density wave (SDW) state can be induced by Fermi surface nesting and electron-electron interaction. It may intertwine with other orders such as charge density wave (CDW), while their relation is still yet to be understood. Here via spin-polarized scanning tunneling microscopy, we directly observed long-range spin modulation on Cr(001) surface, which corresponds to the well-known incommensurate SDW of bulk Cr. It displays 6.0 nm in-plane period and anti-phase behavior between adjacent (001) planes. Meanwhile, we simultaneously observed the coexisting CDW with half the period of SDW. Such SDW/CDW have highly correlated domain structures and are in-phase. Surprisingly, the CDW displays a contrast inversion around a density-of-states dip at -22 meV, indicating an anomalous CDW gap opened below E<sub>F</sub>. These observations support that the CDW is a secondary order driven by SDW. Our work is not only a real-space characterization of incommensurate SDW, but also provides insights on how SDW and CDW coexist.