Helical vortical effects, helical waves, and anomalies of Dirac fermions

Abstract : Helicity is a classically conserved quantity which can be used, in addition to and independently of the (vector) charge and chirality, to characterize thermodynamic ensembles of massless Dirac fermions. We identify a symmetry of the Dirac Lagrangian which is responsible, via the Noether theorem, to the classical conservation of the helicity current. We demonstrate the existence of new nondissipative transport phenomena, helical vortical effects, that emerge in a helically-imbalanced rotating fermionic system. These phenomena lead to appearance of a new gapless hydrodynamic excitation, the helical vortical wave. Our results also imply that the helical symmetry suffers from a quantum anomaly. We conjecture the existence of a new type of triangle anomalies in QED which involve the helicity currents in addition to the standard vector and axial currents.
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Submitted on : Tuesday, January 21, 2020 - 9:22:49 PM
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Victor E. Ambrus, M.N. Chernodub. Helical vortical effects, helical waves, and anomalies of Dirac fermions. 2020. ⟨hal-02447887⟩



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