Frenetic origin of negative differential response

Area of Science:

• Non-equilibrium statistical mechanics
• Theoretical physics
• Chemical kinetics

Background:

• The Green-Kubo formula is a cornerstone for calculating linear response coefficients in equilibrium systems.
• Extending these concepts to non-equilibrium dynamics presents significant theoretical challenges.
• Negative differential conductivity (NDC) is a phenomenon observed in some systems away from equilibrium.

Purpose of the Study:

• To modify the Green-Kubo formula for non-equilibrium dynamics.
• To provide a unifying framework for understanding negative differential response.
• To elucidate the role of 'frenetic contribution' in non-equilibrium transport phenomena.

Main Methods:

• Modification of the Green-Kubo formula for non-equilibrium conditions.
• Development of a theoretical framework based on 'frenetic contribution'.
• Analysis of time-symmetric kinetic effects, including escape rates and reactivities.

Main Results:

• The modified formula allows for the existence of negative differential conductivities away from equilibrium.
• Negative differential response is explained by a negative dependence of escape rates and reactivities on driving forces.
• Partial caging and reduced dynamical activity with increased driving lead to a drop in current.

Conclusions:

• The frenetic contribution offers a unified explanation for negative differential response in non-equilibrium systems.
• Time-symmetric kinetic effects are crucial for understanding current behavior under driving forces.
• The findings have implications for particle and energy transport studies in non-equilibrium systems.