Chiral Magnetic Effect: A Brief Introduction

Chirality of fermions is linked to topology of gauge fields by the index theorem and chiral anomaly. While the chiral anomaly is traditionally associated with the short-distance behavior in quantum field theory, recently, it has been realized that it also affects the macroscopic behavior of systems with chiral fermions. In particular, the local chiral imbalance in the presence of a magnetic field induces non-dissipative transport of electric charge (“the chiral magnetic effect,” CME). In heavy ion collisions, there is an ongoing search for this effect at Relativistic Heavy Ion Collider at BNL and Large Hadron Collider at CERN, with results from a dedicated isobar run presented very recently by the STAR Collaboration. An observation of CME in heavy ion collisions could shed light on the mechanism of baryon asymmetry generation in the Early Universe. For the case of an Abelian gauge theory, the CME has been already discovered in Dirac and Weyl semimetals possessing chiral quasi-particles. This observation opens a path toward new applications, including chiral qubits.