Fig. 4: Experimental protocol for observing the spectral localizer.
From: Revealing topology in metals using experimental protocols inspired by K-theory
a Schematic of the spectrally localized phononic metamaterial with the domain wall shown. The two sublattices of the system are indicated in magenta and cyan, which correspond to entries of + 1 and − 1 in Π, respectively. b The configurations of the system when the localizer is centered at x = − 11, x = 0, and x = 9. The height of each resonator above 38 mm is indicated by the color scale. As the underlying phononic topological metal in Fig. 3 uses resonators that are 40 mm tall, and small changes to the resonator volume change its frequency without changing its couplings, this coloration is effectively showing the on-site potential added in Eq. (6).
