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Dispersionless Flat Mode and Vibrational Anomaly in Active Brownian Vibrators Induced by Stringlike Dynamical Defects
Cunyuan Jiang1,2,3, Zihan Zheng1,4, Yangrui Chen1,4
1School of Physics and Astronomy, <a href="https://ror.org/0220qvk04">Shanghai Jiao Tong University</a>, Shanghai 200240, China.
Physical Review Letters
|November 15, 2024
Summary
Active Brownian particles exhibit a novel low-energy "flat mode," causing excess vibrations beyond standard models. This collective excitation originates from stringlike defects in granular assemblies, offering new insights into active matter physics.
Area of Science:
- Active matter physics
- Soft condensed matter
Background:
- Active Brownian particles model self-propelled systems.
- Understanding collective behavior mechanisms is crucial.
Purpose of the Study:
- Investigate collective excitations in active Brownian vibrators.
- Identify the origin of anomalous vibrational properties.
Main Methods:
- Studied a 2D bidisperse granular assembly of active Brownian vibrators.
- Analyzed the transverse spectrum and vibrational density of states (VDOS).
- Explored parameter space: packing fraction, frequency, size ratio, mixture ratio.
Main Results:
- Discovered a low-energy
- flat mode
- in the transverse spectrum.
- Observed an anomalous excess in VDOS beyond the Debye contribution.
- Identified stringlike dynamical defects as the microscopic origin of the flat mode.
Conclusions:
- The flat mode is a key collective excitation in active Brownian vibrators.
- Dynamical defects drive anomalous vibrational behavior in active matter.
- Findings provide insights into the physics of disordered systems and active matter.
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