Fig. 2

Sample design and experimental protocols. The membranes are schematized by a colored square containing a heater in red and a thermometer in blue. Several experimental protocols have been used, a where the temperature gradient is established through a DC current applied to the heater on the right membrane creating a continuous heat flow to the left membrane through the 1D phonon waveguide. The two temperatures T₁ and T₂ are measured with the two thermometers and b the DC current is supplied to the heater on the left membrane, the heat flow is then reversed as compared to the case a. The two first protocols (a, b) have been established to verify the symmetry of heat transport in the nanowires. In protocol c, one of the nanowires has been cut by FIB, then the steps a, b are repeated to check the additivity of the heat flow and potentially to probe the number of conducting channels in each nanowire. In d both nanowires have been cut to measure the thermal conductance K_b1,2 of the suspending beams of a single membrane