Extended Data Fig. 9: Local twist angle estimation procedure.

Procedure for extracting the local change in twist angle from dynamic simulations of atomic motion. (a) Definition of radial distance r and tangential displacement u: local twist is defined to be du/dr in the limit r → 0. (b) Snapshot of the change in tangential displacement versus radial distance 0.9 ps after pumping the 2° WSe₂/MoSe₂ sample, coinciding in time with the first peak of the oscillation. Dots show atomic positions, the solid line the best fifth order polynomial fit used to compute the derivate at r = 0. Note that the tangential component of the displacement field is not single valued as a function of distance from the vortex center because the displacement field has only three-fold discrete rotational symmetry, rather than continuous rotational symmetry. The variance increases the greater the radial distance and there is consequently no improvement to the goodness of fit at polynomial orders higher than fifth. (c) A second snapshot 1.8 ps following pump arrival, coinciding with the first trough in the oscillation.