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Phase Coexistence in Two-Dimensional Passive and Active Dumbbell Systems
Leticia F Cugliandolo1,2, Pasquale Digregorio3, Giuseppe Gonnella3
1Sorbonne Universités, Université Pierre et Marie Curie-Paris VI, Laboratoire de Physique Théorique et Hautes Énergies, 4 Place Jussieu, 75252 Paris Cedex 05, France.
Active dumbbell systems show coexistence between ordered and disordered phases. This behavior persists in the passive limit, similar to disk systems, without abrupt changes from increased activity.
Area of Science:
- Condensed matter physics
- Statistical mechanics
- Soft matter physics
Background:
- Understanding phase transitions in two-dimensional systems is crucial.
- Active matter systems exhibit unique collective behaviors distinct from passive systems.
- Hexatic order, a distinct phase between solid and liquid, is observed in 2D systems.
Purpose of the Study:
- To investigate the coexistence of hexatic order with liquid or gas phases in active dumbbell systems.
- To compare the behavior of active dumbbell systems with passive systems (hard and soft disks).
- To determine the effect of increasing activity on phase transitions.
Main Methods:
- Simulations of active dumbbell systems with repulsive power-law interactions in two dimensions.
- Analysis of phase coexistence over a range of packing fractions.
- Examination of system behavior in the passive limit and with increasing activity.
Main Results:
- Macroscopic coexistence of hexatic order with liquid/gas phases was observed over a finite packing fraction interval.
- This coexistence interval remained finite in the passive limit, mirroring findings in hard and soft disk systems.
- No discontinuous behavior was detected when increasing activity from the passive limit.
Conclusions:
- Active dumbbell systems exhibit unique phase behavior characterized by macroscopic coexistence.
- The observed phenomena are consistent with, yet distinct from, passive 2D systems.
- Activity in these systems does not induce abrupt phase transitions from the passive state.
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