Negative interlayer shear effect on a double-layered van der Waals material resonator

In sharp contrast to the previous view that interlayer shear enhances bending stiffness of van der Waals material, here we report a decreasing bending stiffness and natural frequency in double-layered ${\mathrm{MoS}}_{2}$ (${\mathrm{DLMoS}}_{2}$) nanoresonators with special stacking orders. Further theoretical analysis shows that the decreasing frequency is mainly due to the negative interlayer shear modulus in ${\mathrm{DLMoS}}_{2}$ nanoresonators with some stacking orders and twisting angles. Detailed analysis of the molecular structure reveals the essential roles of the interfacial potential in the interlayer shear modulus. The present study provides valuable physical insights for understanding the mechanical behaviors of double-layered van der Waals material resonators.