Vortical effects in Dirac fluids with vector, chiral and helical charges

Understand

Helicity of free massless Dirac fermions is a conserved, Lorentz-invariant quantity at the level of the classical equations of motion.

• For a generic ensemble consisting of particles and antiparticles, the helical and chiral charges are different conserved quantities.
• The flow of helicity can be modelled by the helicity current, which is again conserved in the absence of interactions.
• Similar to the axial vortical effect which generates an axial (chiral) current, the helicity current is induced by vorticity in a finite temperature medium with vector (electrical) charge imbalance via the helical vortical effects, leading to new nondissipative transport phenomena.