Molecular dynamics simulations, performed with chemically
accurateab initiomachine-learning force fields,
are used to demonstrate
that layer stiffness has profound effects on the superlubricant state
of two-dimensional van der Waals heterostructures. We engineer bilayers
of different rigidity but identical interlayer sliding energy surface
and show that a 2-fold increase in the intralayer stiffness reduces
the friction by a factor of ∼6. Two sliding regimes as a function
of the sliding velocity are found. At a low velocity, the heat generated
by the motion is efficiently exchanged between the layers and the
friction is independent of the layer order. In contrast, at a high
velocity, the friction heat flux cannot be exchanged fast enough and
a buildup of significant temperature gradients between the layers
is observed. In this situation, the temperature profile depends on
whether the slider is softer than the substrate.