Experiment of 1D spring-mass system. a Setup scheme. b Actual picture of the experimental setup. c Ratio between displacement amplitudes of masses m and M
0 for a single unit cell. d
Left-hand side shows the dispersion relation predicted (q is the Bloch wave-vector and a is the lattice constant). Right-hand side shows the transmittance for the whole system and the negative transmittance indicates a negative mass density.