Experimental observation of gapped shear waves and liquid-like to gas-like dynamical crossover in active granular matter
arXiv:2403.08285 · doi:10.1038/s42005-025-02008-1
Abstract
Unlike crystalline solids, liquids lack long-range order, resulting in diffusive shear fluctuations rather than propagating waves. Simulations predict that liquids exhibit a -gap in wave-vector space, where solid-like transverse waves reappear above this gap. Experimental evidence in classical liquids has been limited, observed only in 2D dusty plasmas. Here, we investigate this phenomenon using active Brownian vibrators and uncover distinct gas-like and liquid-like phases depending on the packing fraction. We measure key properties, including pair correlation functions, mean square displacements, velocity auto-correlation functions, and vibrational density of states. In the liquid-like phase, we confirm the -gap in transverse excitations, whose size grows as the packing fraction decreases and eventually disappears in the gas phase. Our findings extend the concept of the -gap to active granular systems and reveal striking parallels with supercritical fluids.
arXiv commentv2: matching the published version
References in corpus (41)
- On dense granular flows
- A constitutive law for dense granular flows
- Jamming at Zero Temperature and Zero Applied Stress: the Epitome of Disorder
- Dynamical clustering and phase separation in suspensions of self-propelled colloidal particles
- Random Packings of Frictionless Particles
- Collective Motion of Vibrated Polar Disks
- Clustering, Order, and Collapse in a Driven Granular Monolayer
- Microscopic dynamics in liquid metals: the experimental point of view
- Flocking at a distance in active granular matter
- Collective modes and thermodynamics of the liquid state
- Velocity statistics in excited granular media
- Granular materials flow like complex fluids
- Elementary excitations and crossover phenomenon in liquids
- Crystallization of a quasi-two-dimensional granular fluid
- "Liquid-gas" transition in the supercritical region: Fundamental changes in the particle dynamics
- Randomly Driven Granular Fluids: large scale structure
- Caging dynamics in a granular fluid
- Flow-induced Agitations Create a Granular Fluid
- Gapped momentum states
- Emergence and evolution of -gap in spectra of liquid and supercritical states
- Velocity distribution of a homogeneously driven two-dimensional granular gas
- Transition in the supercritical state of matter: experimental evidence
- Flocking without alignment interactions in attractive active Brownian particles
- Velocity Fluctuations in Electrostatically Driven Granular Media
- Universal law for the vibrational density of states of liquids
- Evidence for structural crossover in the supercritical state
- Hydrodynamic modes in a confined granular fluid
- Fluctuating hydrodynamics and correlation lengths in a driven granular fluid
- Onset of transverse (shear) waves in strongly-coupled Yukawa fluids
- Collective modes and gapped momentum states in liquid Ga: experiment, theory and simulation
- Disentangling boson peaks and Van Hove singularities in a model glass
- Experimental Confirmation of the Universal Law for the Vibrational Density of States of Liquids
- Hydrodynamic Correlation Functions of a Driven Granular Fluid in Steady State
- Collective modes of two-dimensional classical Coulomb fluids
- Spontaneous Demixing of Binary Colloidal Flocks
- Disorder-induced vibrational anomalies from crystalline to amorphous solids
- High-energy velocity tails in uniformly heated granular materials
- Onset of two collective excitations in the transverse dynamics of a simple fluid
- Observation of fast sound in two-dimensional dusty plasma liquids
- Level statistics and Anderson delocalization in two-dimensional granular materials
- Tuning the distance to the equipartition by controlling the collision rate in a driven granular gas experiment
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- Revisiting the phonon theory of liquid heat capacity: low-frequency shear modes and intramolecular vibrations
- Simple holographic dual of the Maxwell-Cattaneo model & the fate of KMS symmetry for non-hydrodynamic modes
- Topological signatures of collective dynamics and turbulent-like energy cascades in apolar active granular
- Particle-scale origin of quadrupolar non-affine displacement fields in granular solids
- Revisiting the question of what instantaneous normal modes tell us about liquid dynamics
- Atomistic mechanisms of viscosity in 2D liquid-like fluids
- Physical Signatures of Supercritical Fluid Boundaries