Unveiling Electronic Behaviors in Heterochiral Charge-Density-Wave Twisted Stacking Materials with 1.25 nm Unit Dependence

Layered charge-density-wave (CDW) materials have gained increasing interest due to their CDW stacking-dependent electronic properties for practical applications. Among the large family of CDW materials, those with sta r of David (SOD) patterns are very important due to the potentials for quantum spin liquid and related device applications. However, the spatial extension and the spin coupling information down to the nanoscale remain elusive. Here , we report the study of heterochiral CDW stack i n g s in bilayer (BL) NbSe2 with high spatial resolution. We reveal that there exist well-defined heterochiral stackings, which have inhomogeneous electronic states among neighboring CDW units (sta r of David, SOD), significantly different from the homogeneous electronic states in the homochiral stackings. Intriguingly, the different electronic behaviors are spatially localized withi n each SOD with a unit size of 1.25 nm, and the gap sizes are determined by the different types of SOD stackings. Density functional theory (DFT) calculations match the experimental measurements wel l and reveal the SOD-stacking-dependent correlated electronic states and antiferromagnetic/ferromagnetic couplings. Our findings give a deep understanding of the spatial distribution of interlayer stacking and the delicate modulation of the spintronic states, which is very helpf u l for CDW-based nanoelectronic devices.

Automated summary

In this study, the heterochiral CDW stackings in bilayer NbSe2 with high spatial resolution were investigated. Well-defined heterochiral stackings were found, which showed significantly different electronic states compared to the homogeneous states in homochiral stackings. The different electronic behaviors were spatially localized within each SOD with a size of 1.25 nm, and the gap sizes were determined by the types of SOD stackings. Density functional theory calculations matched the experimental measurements well and revealed the SOD-stacking-dependent correlated electronic states and antiferromagnetic/ferromagnetic couplings. These findings provide a deep understanding of the spatial distribution of interlayer stacking and the modulation of spintronic states, which is helpful for CDW-based nanoelectronic devices.