Fig. 4: Experimental evidence for the double-helicoid surface arcs around \({\bar{\mathbf{\Gamma }}}\).
From: Observation of quadratic Weyl points and double-helicoid arcs
a Experimental setup for surface measurements. b 2D Fourier transformations (color scale) of the measured surface fields at different frequencies, compared with the numerical isofrequency contours of the topological surface states (red lines). As before, the color spheres highlight the projected Weyl nodes, and the shaded areas are the projected bulk bands. c Schematic illustration of the surface arc connectivity between one charge-2 QWP and two charge-1 CWPs in our system (top), compared with that between the spin-1 Weyl point and charge-2 Dirac point in recent studies12,29 (bottom). d Surface spectrum extracted along the loop of radius \(0.5\pi /a\) centered at \({\bar{\mathrm{\Gamma }}}\). e Surface spectrum extracted along the loop of radius \(0.43\pi /a\) centered at \({\bar{\mathrm{H}}}\).
