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Free keywords:
Anisotropy, Calculations, Charge density, Charge density waves, Electronic structure, Metal insulator boundaries, Semiconductor insulator boundaries, Transition metals, Van der Waals forces, Ab initio calculations, Emergent phenomenon, Interlayer interactions, Layered transition metal dichalcogenides, Quasi-one dimensional, Resistivity anisotropy, Two-dimensional materials, Van der waals, Metal insulator transition
Abstract:
Layered transition metal dichalcogenides (TMDs) are commonly classified as quasi-two-dimensional materials, meaning that their electronic structure closely resembles that of an individual layer, which results in resistivity anisotropies reaching thousands. Here, we show that this rule does not hold for 1T-TaS2—a compound with the richest phase diagram among TMDs. Although the onset of charge density wave order makes the in-plane conduction non-metallic, we reveal that the out-of-plane charge transport is metallic and the resistivity anisotropy is close to one. We support our findings with ab initio calculations predicting a pronounced quasi-one-dimensional character of the electronic structure. Consequently, we interpret the highly debated metal-insulator transition in 1T-TaS2 as a quasi-one-dimensional instability, contrary to the long-standing Mott localisation picture. In a broader context, these findings are relevant for the newly born field of van der Waals heterostructures, where tuning interlayer interactions (e.g., by twist, strain, intercalation, etc.) leads to new emergent phenomena. © 2020, The Author(s).
