# Fermion condensate

In a theory with two chiral fields, ψ

_{1} and ψ

_{2} with a global symmetry relating the relative phases of both fields, but at low temperatures, the correlation function is nonzero, then we say a

**fermion condensate** (also called chiral condensate) has formed. For example, in

QCD, there is an approximate (so there's no real

spontaneous symmetry breaking; the

VEV will always be aligned in a fixed direction) axial symmetry which is broken because the

quarks form a chiral condensate. See

Technicolor (physics) for another example.

BCS in

superconductivity is another.

To get a "feel" for chiral condensates, a good toy model to start with is the Schwinger model.