Abstract
Crystalline defects can modify quantum interactions in solids, causing unintuitive, even favourable, properties such as quantum Hall effect or superconducting vortex pinning. Here we present another example of this notion—an unexpected unidirectional Kondo scattering in single crystals of 2H-NbS2. This manifests as a pronounced low-temperature enhancement in the out-of-plane resistivity and thermopower below 40 K, hidden for the in-plane charge transport. The anomaly can be suppressed by the c-axis-oriented magnetic field, but is unaffected by field applied along the planes. The magnetic moments originate from layers of 1T-NbS2, which inevitably form during the growth, undergoing a charge-density-wave reconstruction with each superlattice cell (David-star-shaped cluster of Nb atoms) hosting a localised spin. Our results demonstrate the unique and highly anisotropic response of a spontaneously formed Kondo-lattice heterostructure, intercalated in a layered conductor.
Highlights
Layered van der Waals materials, such as transition metal dichalcogenides (TMDs), have attracted major interest, thanks to their rich variety of ground states and the possibility of their exfoliation down to an atomically thin level, which remarkably modifies their electronic properties[1,2]
Examples include the outstanding stability of interlayer excitons in semiconducting TMDs3, and strongly correlated states in twisted bilayer systems[4]
Relevant aspects of the inter-plane coupling can be deduced by probing out-of-plane charge transport, even in bulk materials[5]
Summary
Layered van der Waals materials, such as transition metal dichalcogenides (TMDs), have attracted major interest, thanks to their rich variety of ground states and the possibility of their exfoliation down to an atomically thin level, which remarkably modifies their electronic properties[1,2]. Enforcing the current flow strictly along the c axis can be rather challenging due to the crystals’ common flake-like appearance and their propensity for delamination. Such a pitfall can distort the measurement results by orders of magnitude, as demonstrated in our recent study of microstructured samples of 1T-TaS2 with a well-defined current flow[6]. This observation motivates a careful re-examination of the out-of-plane charge transport properties in this class of materials by adopting the latest state-of-the-art for quantum matter microfabrication[7]
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