Fig. 2

Characterisation of the microstructure and comparison with the model. a, b Images of the initial (a) and final (b) states of the experiment in Fig. 1b, with colour-coding of the particles according to the number of neighbours n. The emergence of a network of strings is visually apparent. c, d Probability p(n) of a particle having n neighbours in the initial (c) and final (d) state. In the final state, p(n) becomes zero for n = 5, 6 and the mean number of neighbours decreases from \(\bar n = 3.4\) to \(\bar n = 2.4\). e Evolution of the order parameters \(\left| {{\mathrm{\Psi }}_2} \right|\) and \(\left| {{\mathrm{\Psi }}_3} \right|\) as a function of the number of cycles N_c. The evolution of the microstructure into a network of strings occurs in ~200 cycles. f Pair-correlation function g(r) as a function of the normalised distance r/a for the initial (blue) and final (red) configurations in experiment. The schematics explain the shift of the second peak upon formation of strings. g Simulation pictures of the initial state (Φ = 0.4). Green lines show the orientation of the quadrupolar deformation. h Simulation pictures of the final state. The structure obtained is strikingly similar to the experimental one. i Pair-correlation function g(r) as a function of the normalised distance r/a obtained from the initial (blue) and final (red) structures in the simulations. As observed in the experiments, in the final state g(r) has a peak around r/a = 4, typical of a string network