Microscopic Signatures of Chern Number Sign Reversal in Twisted Bilayer WSe_{2}

The observation of quantized Chern numbers in twisted transition metal dichalcogenide homobilayers, including 3.7° twisted MoTe_{2} and 1.23° twisted WSe_{2}, represents a landmark breakthrough in moiré physics. A striking and unresolved paradox to emerge from these studies is the unexpected opposite sign of the measured Chern numbers between the two systems, a discrepancy that strongly hints at a twist-angle-dependent reversal of the Chern number sign. Despite this compelling implication, direct experimental validation of such a sign reversal within a single twisted transition metal dichalcogenide homobilayer system is still elusive. Here, we report the first experimental demonstration that the Chern numbers of the moiré frontier bands undergo sign reversal at a critical twist angle ∼1.42° in twisted WSe_{2} bilayers (tWSe_{2}). Using scanning tunneling microscopy and spectroscopy, we directly measure layer-pseudospin skyrmion textures of tWSe_{2} and our results reveal that tWSe_{2} in the vicinity of the 1.42° exhibits a twist-angle-dependent layer-pseudospin polarization, an effect that serves as the fundamental origin of the observed Chern number sign reversal.