Encoding multistate charge order and chirality in endotaxial heterostructures.

High-density phase change memory (PCM) storage is proposed for materials with multiple intermediate resistance states, which have been observed in 1T-TaS due to charge density wave (CDW) phase transitions. However, the metastability responsible for this behavior makes the presence of multistate switching unpredictable in TaS devices. Here, we demonstrate the fabrication of nanothick verti-lateral H-TaS/1T-TaS heterostructures in which the number of endotaxial metallic H-TaS monolayers dictates the number of resistance transitions in 1T-TaS lamellae near room temperature. Further, we also observe optically active heterochirality in the CDW superlattice structure, which is modulated in concert with the resistivity steps, and we show how strain engineering can be used to nucleate these polytype conversions. This work positions the principle of endotaxial heterostructures as a promising conceptual framework for reliable, non-volatile, and multi-level switching of structure, chirality, and resistance.