Disorder-Induced Long-Ranged Correlations in Scalar Active Matter

Area of Science:

• Physics
• Soft Matter Physics
• Statistical Mechanics

Background:

• Scalar active matter systems exhibit motility-induced phase separation (MIPS).
• Quenched random potentials and torques can significantly alter system dynamics and phase behavior.

Purpose of the Study:

• To investigate the effects of quenched random potentials and torques on scalar active matter.
• To determine the critical dimension for phase separation in disordered active matter systems.

Main Methods:

• Microscopic simulations of scalar active matter.
• Phenomenological modeling.
• Field-theoretical treatment.

Main Results:

• In two dimensions, MIPS is replaced by a homogeneous phase with anomalous long-ranged correlations and nonvanishing steady-state currents.
• A lower-critical dimension (dc=4) is identified, below which phase separation is limited by the Imry-Ma length scale.
• A weak-disorder regime with structure factor S(q) ~ 1/q^2 is identified, consistent with numerical results.

Conclusions:

• Disorder fundamentally alters phase behavior in active matter, replacing MIPS with novel homogeneous phases.
• The critical dimension of four dictates the prevalence of phase separation versus homogeneous disordered phases.
• Distinct weak and strong disorder regimes govern system behavior depending on dimensionality and potential strength.