Chiral magnetic effect (CME) is the generation of electric current along an external magnetic field induced by chirality imbalance. Fermions are said to be chiral if they keep a definite projection of spin quantum number on momentum. The CME is a macroscopic quantum phenomenon present in systems with charged chiral fermions, such as the quark-gluon plasma, or Dirac and Weyl semimetals.

The CME is a consequence of chiral anomaly in quantum field theory; unlike conventional superconductivity or superfluidity, it does not require a spontaneous symmetry breaking. The chiral magnetic current is non-dissipative because it is topologically protected: the imbalance between the densities of left-handed and right-handed chiral fermions is linked to the topology of fields in gauge theory by the Atiyah-Singer index theorem.

The experimental observation of CME in a Dirac semimetal ZrTe5 was reported in 2014 by a group from Brookhaven National Laboratory and Stony Brook University. The material showed a conductivity increase in the Lorentz force-free configuration of the parallel magnetic and electric fields.

In 2015, the STAR detector at Relativistic Heavy Ion Collider, Brookhaven National Laboratory and ALICE: A Large Ion Collider Experiment at the Large Hadron Collider, CERN presented an experimental evidence for the existence of CME in the quark-gluon plasma.

 

Note:   The above text is excerpted from the Wikipedia article Chiral magnetic effect, which has been released under the GNU Free Documentation License.