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

Abstract

The massless fermions of a Weyl 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 à and a single chirality AE 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 ∂j=∂B ¼ AEðe à e=h 2 Þμ along the magnetic field at chemical potential μ.

Majorana-Hubbard model on the square lattice

“…We only have one Dirac fermion in the lowenergy theory at the cost of U (1) symmetry only being emergent instead of an exact lattice symmetry. Such Majorana models might be useful for high energy physics simulations [42].…”

Transport through Andreev bound states in a Weyl semimetal quantum dot

“…A quantum dot made of WSM material in the presence of superconductors is of particular interest due to the distinctive nature of transport at a WSM-Superconductor (SC) interface 13,21,[30][31][32] and provides the possibility of capturing the otherwise elusive physics associated with the chiral excitation in the WSM 30 . In this manuscript we study transport through the Andreev states of a WSM quantum dot in a simple setup where we sandwich the dot in between a superconductor and a normal lead (see Fig.…”

Universal chiral magnetic effect in the vortex lattice of a Weyl superconductor

“…Because superconductivity breaks gauge invariance, a Weyl superconductor is not so constrained: As demonstrated in Ref. 8, one of the two chiralities can be gapped out by the superconducting order parameter. When a magnetic flux Φ penetrates uniformly through a thin film (no vortices), an equilibrium current…”