Holographic Weyl semimetals with dislocations

Abstract: Weyl semimetals (WSMs) represent three-dimensional gapless topological states of matter characterized by the monopole-antimonopole pairs of the Abelian Berry curvature at the band-touching points in the momentum space. As a consequence, they display chiral anomalies that can be realized through a crystalline dislocation defect associated with the discrete lattice translational symmetry. Using the last two features of WSMs as our guiding principles, we construct a holographic WSM with dislocations by utilizing the ($4+1$)-dimensional Chern-Simons gravitational theory in anti-de Sitter spacetime. This theory encodes the chiral anomaly and incorporates torsion, thereby holographically capturing lattice dislocation defects. By explicitly solving the equations of motion employing the asymptotic expansion near the boundary, we show that such a theory at the ($3+1$)-dimensional spacetime boundary possesses axially-symmetric solutions that can be interpreted as holographic WSMs with dislocation defects at finite temperature, encoded through a black hole in the bulk gravity. Such solutions, at the same time, feature the chiral anomaly proportional to the Nieh-Yan invariant. Our results should therefore motivate future studies of the holographic topological phases by employing bulk gravitational Chern-Simons theories and establishing torsion as a holographic counterpart of crystalline dislocation defects.