{{Short description|Macroscopic quantum phenomenon involving electric current}} [[File:Chiral magnetic effect ZrTe5 - resistivity vs magnetic field vs angle at 20K.svg|thumb|alt=Graph of resistivity vs applied magnetic field strength in zirconium pentatelluride|Resistivity increases in a slab of zirconium pentatelluride with the strength of the applied magnetic field for all angles between the current and the field but the angle of 0° when they are parallel: in this configuration of the fields a chiral non-dissipative current appears.]] '''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.<ref name="Review">{{cite journal|author=D. Kharzeev|title=The Chiral Magnetic Effect and anomaly-induced transport|journal=Progress in Particle and Nuclear Physics|volume=75|pages=133–151|year=2014|doi=10.1016/j.ppnp.2014.01.002|arxiv=1312.3348|bibcode=2014PrPNP..75..133K|s2cid=118508661}}</ref> 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, zirconium pentatelluride (ZrTe<sub>5</sub>), was reported in 2014 by a group from Brookhaven National Laboratory and Stony Brook University.<ref name="ExpObs">{{cite journal|vauthors=Li Q, Kharzeev DE, Zhang C, Huang Y, Pletikosic I, Fedorov AV, Zhong RD, Schneeloch JA, Gu GD, Valla T|title=Chiral magnetic effect in ZrTe5|journal=Nature Physics|volume=12|issue=6|pages=550–554|year=2016|doi=10.1038/nphys3648|arxiv=1412.6543|bibcode=2016NatPh..12..550L|s2cid=99424051}}</ref><ref name="Media">{{cite web|url=http://phys.org/news/2016-02-chiral-magnetic-effect-quantum-current.html|title=Chiral magnetic effect generates quantum current|publisher=Phys.org|author=Brookhaven National Laboratory|date=8 February 2016|access-date=4 Jan 2019}}</ref> 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 Brookhaven's Relativistic Heavy Ion Collider<ref name="ExpNuc">{{cite journal|author=L. Adamczyk|collaboration=STAR Collaboration|title=Observation of charge asymmetry dependence of pion elliptic flow and the possible chiral magnetic wave in heavy-ion collisions|journal=Physical Review Letters|volume=114|issue = 25|article-number=252302|year=2015|doi=10.1103/PhysRevLett.114.252302|pmid=26197122|arxiv=1504.02175|bibcode=2015PhRvL.114y2302A|s2cid=13186933}}</ref> and ALICE at CERN<ref name="ALICE">{{cite journal|author=R. Belmont|collaboration=ALICE Collaboration|title=Charge-dependent anisotropic flow studies and the search for the Chiral Magnetic Wave in ALICE|journal=Nuclear Physics A|volume=931|page=981|year=2014|doi=10.1016/j.nuclphysa.2014.09.070|arxiv=1408.1043|bibcode=2014NuPhA.931..981B|s2cid=118833403}}</ref> presented experimental evidence for the existence of CME in the quark–gluon plasma.<ref name="CMW">{{cite web|url=http://phys.org/news/2015-06-scientists-ripples-particle-separating-primordial-plasma.html|title=Scientists see ripples of a particle-separating wave in primordial plasma|publisher=Phys.org|date=8 June 2015|author=Brookhaven National Laboratory|access-date=4 Jan 2019}}</ref>
==See also== * Euler–Heisenberg Lagrangian * Chiral anomaly
==References== {{Reflist}}
Category:Electricity Category:Condensed matter physics Category:Quantum field theory