Detecting spin-crossover transitions with two-dimensional materials.

Spin-crossover (SCO) materials are metal complexes where the spin state of the metallic center changes between high-spin (HS) and low-spin (LS) due to the presence of an external stimulus (light, pressure, temperature…), with potential applications as memory devices or in spintronic applications [1].

In this work, we fabricate hybrid van der Waals heterostructures based on SCO and inorganic two-dimensional (2D) materials. First, we exfoliate mechanically a SCO compound and characterize it by atomic force microscopy, optical microscopy and Raman spectroscopy. Then, these molecular flakes are deterministically combined with inorganic 2D systems like few-layers graphene (FLG) or atomically-thin layers of 2H-NbSe₂ and WSe₂, thus creating hybrid van der Waals heterostructures. Interestingly, the hysteretic thermal spin transition is detected by transport measurements in SCO/FLG heterostructures and by photoluminescence in SCO/WSe₂ heterostructures.

Our results illustrate the synergy between the SCO and the inorganic system and opens the door to explore further molecular compounds of interest which properties could not be detected otherwise.

References
[1] Dugay, J. et al., Nano Letters 17, 186-193 (2017).