Color Superconductivity and Charge Neutrality in Yukawa Theory

Area of Science:

• Condensed matter physics
• Quantum chromodynamics
• High-energy nuclear physics

Background:

• Cooper pairing in two-species fermion systems is typically assumed to maintain charge neutrality.
• This assumption is based on mean-field calculations with zero-range interactions, where self-energy is energy and momentum independent.

Purpose of the Study:

• To investigate the neutrality of two-species condensates using a Yukawa model with finite-range interactions.
• To determine if energy-momentum dependence of self-energy affects population balance under chemical potential stress.

Main Methods:

• Employed a Yukawa model with finite-range interactions.
• Performed mean-field calculations to derive the energy-momentum dependence of the self-energy.
• Analyzed the impact of species-dependent chemical potential on the Cooper-paired phase.

Main Results:

• The energy dependence of the self-energy was fully obtained.
• A population imbalance was observed in the Cooper-paired phase when subjected to a species-dependent chemical potential.
• Deviations from neutrality were confirmed in a system with finite-range interactions.

Conclusions:

• The belief in inherent neutrality of two-species Cooper pairing may be incorrect.
• The findings support the possibility that color-flavor-locked quark matter is not an insulator.
• Finite-range interactions play a crucial role in determining the properties of such condensates.