Fig. 2: Quadrupole topological phases in heat transport solely induced by Hermitian advection.
From: Observation of bulk quadrupole in topological heat transport
a Photo of a fabricated sample with 9 square-lattices made of epoxy resin, while water is fully imposed to each site as the working fluid. The left and right upper insets present the connection of a fabricated unit-structure and one square lattice with 16 sites. The grey-shadowed and black-dashed areas respectively indicate the over-coupling and under-coupling channels. The green arrows indicate the directions of the imposed advections. b Spectra of the thermal quadrupole topological phases. c Measured temperature field intensities at corresponding boundaries. The measured regions are marked by colored borders in (a). d–f Captured temperature distributions at steady state after the field evolutions at the peaks of the corner, edge, and bulk spectra as indicated by the red, blue, and black dashed lines in (c), and their locations are indicated by the dashed white lines in d–f.
