Torsional Chiral Magnetic Effect in a Weyl Semimetal with a Topological Defect

Abstract

We propose a torsional response raised by lattice dislocation in Weyl semimetals akin to chiral magnetic effect; i.e. a fictitious magnetic field arising from screw or edge dislocation induces charge current. We demonstrate that, in sharp contrast to the usual chiral magnetic effect which vanishes in real solid state materials, the torsional chiral magnetic effect exists even for realistic lattice models, which implies the experimental detection of the effect via SQUID or nonlocal resistivity measurements in Weyl semimetal materials. 11.30.Rd, 11.15.Yc Recently, many candidate materials for Dirac semimetals and Weyl semimetals (WSMs) [1][2][3][4], have been discovered [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. These topological semimetals are intriguing because of exotic transport phenomena associated with the chiral anomaly in quantum field theory [24], such as the anomalous Hall effect [25,26], chiral magnetic effect (CME) [27], negative longitudinal magnetoresistance [5, 12, 19-21, 28, 29], and chiral gauge field [30].Among them, the CME has been discussed in broad areas of quantum many-body physics, including nuclear and nonequilibrium physics as well as condensed matter physics. It is the generation of charge current parallel to an applied magnetic field even in the absence of electric fields. In nuclear physics, together with the chiral vortical effect [31], it is expected to play an important role in heavy ion collisions experiments [32,33]. The CME also caused a stir in nonequilibrium statistical physics, since it leads to the existence of the ground state which, recently, attracts a renewed interest in connection with the realization of quantum time crystal [34], and then the CME has been studied from this point of view [35,36]. However, unfortunately, their results are negative for its realization: the macroscopic ground state current in realistic WSMs is always absent.In this letter, we propose a chiral response in WSMs, named "torsional chiral magnetic effect (TCME)", in which the ground state charge current is caused by the effective magnetic field induced by lattice dislocation as shown in FIG.1. By using the Cartan formalism of the differential geometry, we can describe the lattice strain and dislocation in terms of vielbein and torsion [37]. From the viewpoint of the quantum field theory in curved space-time, the TCME is raised by the mixed action of electromagnetic and torsional fields that is prohibited in four-dimensional spacetime with the Lorentz symmetry, but made possible in non-relativistic band electrons in solid state systems. Furthermore, we demonstrate that the TCME is possible in realistic lattice models by carrying out numerical calculations. Our results imply the existence of experimentally observable current induced by the TCME in real WSM materials. We also resolve the relation between our results and the no-go theorem that the CME is absent in equilibrium states [35,36]. First of all, we clarify the notations. The indices i, j, · · · = x, y, z a...

Landau levels from neutral Bogoliubov particles in two-dimensional nodal superconductors under strain and doping gradients

“…Examples include d x 2 −y 2 cuprates and odd-parity p-wave cases. In view of similar proposals for pseudo-magnetic fields in Weyl semi-metals [10][11][12][13][14][15]28], such effects are also likely to occur in more complicated 3D systems.…”

“…In contrast to genuine magnetic fields in a SC, there are no induced currents and no screening associated with the Meissner effect. Our work is motivated by interesting developments in graphene [8] where strain-induced pseudo-magnetic fields lead to Landau quantization and quantum oscillations, which were already observed in experiment [9], and more recent proposals in the context of Dirac and Weyl semimetals [10][11][12][13][14][15].A possible experimental setup is shown in Fig. 1.…”

Quantum oscillations without magnetic field

“…In graphene, for instance, the effect of curvature is famously analogous to a pseudomagnetic field [21] that can be quite large and is known to generate pronounced Landau levels observed in the tunneling spectroscopy [22]. Recent theoretical work [23][24][25][26][27] showed that similar effects can be anticipated in three-dimensional Dirac and Weyl semimetals, although the estimated field strengths in the geometries that have been considered are rather small (below 1 Tesla in Ref. [26]).…”

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

“…(For such a spatial separation of counterpropagating particle currents in the normal state, see Refs. [53][54][55]). …”