Superconductivity Provides Access to the Chiral Magnetic Effect of an Unpaired Weyl Cone

The massless fermions of aWeyl semimetal come in two species of opposite chirality, in two cones of the band structure. As a consequence, the current j induced in one Weyl cone by a magnetic field B [the chiral magnetic effect (CME)] is canceled in equilibrium by an opposite current in the other cone. Here, we show that superconductivity offers a way to avoid this cancellation, by means of a flux bias that gaps out a Weyl cone jointly with its particle-hole conjugate. The remaining gapless Weyl cone and its particle-hole conjugate represent a single fermionic species, with renormalized charge e* and a single chirality +/- set by the sign of the flux bias. As a consequence, the CME is no longer canceled in equilibrium but appears as a supercurrent response partial derivative j/partial derivative B = +/-(e*e/h(2))mu along the magnetic field at chemical potential mu.