Probing and Sensing Layer-Dependent van der Waals Interaction via Induced Anisotropy

Van der Waals (vdW) interaction, a fundamental force, plays an important role in two-dimensional (2D) systems by enabling atomically sharp assemblies and giving rise to many emergent phenomena. However, experimentally probing and sensing the evolution of vdW interaction between 2D layers remains challenging due to its extreme weakness, very short range, and the difficulty of keeping two atomic layers perfectly parallel while finely adjusting the interaction. Here, we demonstrate an optical strategy to indirectly probe vdW interactions by exploiting induced anisotropy in MoS2/NbIrTe4 heterostructures. We construct heterostructures using isotropic MoS2 and anisotropic NbIrTe4 to ensure perfect parallelism. We modulate and probe the vdW interaction by varying the NbIrTe4 thickness and monitor the vdW-interaction-induced anisotropy in MoS2. We find such induced anisotropy to strongly depend on the NbIrTe4 thickness and clearly observe its fast-decaying nature. This work provides a simple, noncontact approach for indirectly probing interlayer vdW interactions.