Fig. 5
From: Observation of emergent momentum–time skyrmions in parity–time-symmetric non-unitary quench dynamics
Experimental results of the \({\cal{P}}{\cal{T}}\)-symmetry-unbroken QW dynamics with a large winding-number difference. a Time-evolution and b spin textures of n(k, t) in momentum–time space for a quench process between the initial non-unitary Floquet operator given by \((\theta _1^{\mathrm{i}} = - \pi /2,\theta _2^{\mathrm{i}} = - \pi /4)\) with νi = −2, and the final one characterized by \(\left( {\theta _1^{\mathrm{f}} = \pi /2,\theta _2^{\mathrm{f}} = - {\mathrm{arcsin}}\left( {\frac{1}{\alpha }{\mathrm{cos}}\frac{\pi }{6}} \right)} \right)\) with νf = 2. The eight fixed points (dashed lines) are located at {−0.5300π, −0.0300π, 0.4699π, 0.9699π} for c− = 0; and {−0.7450π, −0.2450π, 0.2550π, 0.7550π} for c+ = 0. The color code represents the value of n3(k, t)
