Mechanisms and degrees of freedom behind CDW and superconductivity in misfit layered chalcogenides

Determine the microscopic mechanisms and the key electronic and lattice degrees of freedom that govern charge-density-wave order and superconductivity in misfit layered chalcogenides (MX)1+δ(TX2), specifically in heterostructures comprising 1H-TaS2 monolayers alternated with rocksalt MS(001) bilayers such as (PbS)1.13TaS2 and (SnS)1.15TaS2.

Background

Misfit layered compounds are van der Waals heterostructures that combine 1H-TaS2 monolayers with rocksalt monochalcogenide bilayers, producing symmetry-mismatched interfaces and moiré superlattices. These systems host both charge-density waves and superconductivity, but the interplay between doping, interlayer coupling, and moiré-induced symmetry breaking complicates the identification of the dominant microscopic drivers.

The present work reports STM/STS measurements and multiscale modeling in (PbS)1.13TaS2 and (SnS)1.15TaS2, finding incommensurate, symmetry-broken CDW states and s-wave superconductivity. Despite these insights, the authors explicitly state that the underlying microscopic mechanisms and key degrees of freedom for these ordered phases in misfit compounds remain unknown, highlighting a broader unresolved problem beyond the specific observations reported.