Wave spectroscopy in a driven granular material

Driven granular media constitute model systems in out-of-equilibrium statistical physics. By assimilating the motions of particles to those atoms, by analogy, one can obtain macroscopic equivalent phase transitions. Here, we study fluid-like and crystal-like two-dimensional states a driven material. In our experimental device, tunable magnetic field induces controls remote interactions between particles. We use high-speed video recordings analyse velocity fluctuations individual stationary regime. Using averaging, find that self-organize into collective excitations characterized dispersion relations frequency-wavenumber space. These findings thus reveal mechanical waves analogous condensed matter phonons propagate media. When coupling is weak, are longitudinal, as expected for phase. stronger, both longitudinal transverse propagate, which typically seen solid-like phases. using spatial distribution their interaction potential. Finally, infer elastic parameters assembly from sound velocities, realizing spectroscopy