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Phases and excitations of active rod-bead mixtures: Simulations and experiments

Soni, H and Kumar, N and Nambisan, J and Gupta, RK and Sood, AK and Ramaswamy, S (2020) Phases and excitations of active rod-bead mixtures: Simulations and experiments. In: Soft Matter, 16 (31). pp. 7210-7221.

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Official URL: https://doi.org/10.1039/c9sm02552a


We present a large-scale numerical study, supplemented by experimental observations, on a quasi-two-dimensional active system of polar rods and spherical beads confined between two horizontal plates and energised by vertical vibration. For a low rod concentration Φr, our observations are consistent with a direct phase transition, as bead concentration Φb is increased, from the isotropic phase to a homogeneous flock. For Φr above a threshold value, an ordered band dense in both rods and beads occurs between the disordered phase and the homogeneous flock, in both experiments and simulations. Within the size ranges accessible, we observe only a single band, whose width increases with Φr. Deep in the ordered state, we observe broken-symmetry "sound"modes and giant number fluctuations. The direction-dependent sound speeds and the scaling of fluctuations are consistent with the predictions of field theories of flocking; sound damping rates show departures from such theories, but the range of wavenumbers explored is modest. At very high densities, we see phase separation into rod-rich and bead-rich regions, both of which move coherently. This journal is © The Royal Society of Chemistry.

Item Type: Journal Article
Publication: Soft Matter
Publisher: Royal Society of Chemistry
Additional Information: The copyright for this article belongs to the Author(S).
Keywords: Phase separation, Broken symmetry; Disordered phase; Horizontal plates; Isotropic phase; Number fluctuations; Scaling of fluctuations; Spherical beads; Vertical vibrations, Vibrations (mechanical), article; excitation; phase separation; phase transition; prediction; simulation; sound; velocity; vibration
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 13 Jan 2023 06:32
Last Modified: 13 Jan 2023 06:32
URI: https://eprints.iisc.ac.in/id/eprint/79100

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