Crystalline chirality and interlocked double hourglass Weyl fermion in polyhedra-intercalated transition metal dichalcogenides

Introducing crystalline chirality into transition metal dichalcogenides (TMDs) has attracted much attention due to its modulation effect on optical properties and the potential to reveal new forms of electronic states. Here, we predict a number of chiral materials by intercalating polyhedra into TMD lattices, finding a type of double hourglass Weyl fermion interlocked with crystalline chirality. The best candidate RhVS (P622) possesses the largest hourglass energy window of ~380 meV, as well as strong optical circular dichroism (CD) in the infrared regime, both of which are tunable by external strains. The chirality is originally induced by the configuration of intercalated polyhedra and then reduced by the rotational atomic displacements triggered by intercalation, as indicated by CD calculations. Our study opens the way of designing chiral materials with spin-split double hourglass Weyl fermions via structural unit intercalation in achiral crystals for future chiral-functionalized optoelectronic and spintronic devices.