Encoding multistate charge order and chirality in endotaxial heterostructures

Intrinsic resistivity changes associated with charge density wave (CDW) phase transitions in 1T-TaS$_2$ hold promise for non-volatile memory and computing devices based on the principle of phase change memory (PCM). High-density PCM storage is proposed for materials with multiple intermediate resistance states, which have been observed in 1T-TaS$_2$. However, the metastability responsible for this behavior makes the presence of multistate switching unpredictable in 1T-TaS$_2$ devices. Here, we demonstrate the synthesis of nanothick verti-lateral 1H-TaS$_2$/1T-TaS$_2$ heterostructures in which the number of endotaxial metallic 1H-TaS$_2$ monolayers dictates the number of high-temperature resistance transitions in 1T-TaS$_2$ lamellae. Further, we also observe optically active heterochirality in the CDW superlattice structure, which is modulated in concert with the resistivity steps. This thermally-induced polytype conversion nucleates at folds and kinks where interlayer translations that relax local strain favorably align 1H and 1T layers. This work positions endotaxial TaS$_2$ heterostructures as prime candidates for non-volatile device schemes implementing coupled switching of structure, chirality, and resistance