Abstract
We study the longitudinal magnetotransport in three-dimensional multi-Weyl semimetals, constituted by a pair of (anti)-monopole of arbitrary integer charge (n), with n = 1,2 and 3 in a crystalline environment. For any n > 1, even though the distribution of the underlying Berry curvature is anisotropic, the corresponding intrinsic component of the longitudinal magnetoconductivity (LMC), bearing the signature of the chiral anomaly, is insensitive to the direction of the external magnetic field (B) and increases as B2, at least when it is sufficiently weak (the semi-classical regime). In addition, the LMC scales as n3 with the monopole charge. We demonstrate these outcomes for two distinct scenarios, namely when inter-particle collisions in the Weyl medium are effectively described by (a) a single and (b) two (corresponding to inter- and intra-valley) scattering times. While in the former situation the contribution to LMC from chiral anomaly is inseparable from the non-anomalous ones, these two contributions are characterized by different time scales in the later construction. Specifically for sufficiently large inter-valley scattering time the LMC is dominated by the anomalous contribution, arising from the chiral anomaly. The predicted scaling of LMC and the signature of chiral anomaly can be observed in recently proposed candidate materials, accommodating multi-Weyl semimetals in various solid state compounds.
Highlights
Preserved, while its chiral counterpart U(1)5 = U(1)L − U(1)R suffers an anomalous violation [8, 9]
We show that the system becomes more conductive with an increasing magnetic field, an effect often refered as negative longitudinal magnetoresistance (LMR), a hallmark signature of the Adler-Jackiw-Bell chiral anomaly [22]
We observe that the dominant longitudinal magnetoconductivity (LMC) for arbitrary n is the one related to the chiral magnetic conductivity. This supports the idea of a direct relation between positive LMC and the chiral anomaly. we show that in presence of two distinct time scales it possible to demonstrate a one-to-one correspondence between LMC and the chiral anomaly when τinter τintra
Summary
We begin the discussion by computing the Berry curvature and the associated integer topological invariant of a multi-Weyl semimetal, featuring Weyl nodes with arbitrary integer monopole charge n. Notice that upon integrating the Berry curvature over a closed surface Σ, we find the integer topological invariant of a multi-Weyl semimetal sn. The integer topological invariant of a Weyl node measures the amount of Berry flux enclosed by a unit area surface, and the Weyl nodes act as source and sink of Abelian Berry curvature of strength n. At this point it is worth pausing to appreciate the dimensionality of various physical quantities in the natural units, in which we set = c = kB = 1. The electric charge has dimension zero, while electric and magnetic fields have dimensions two, v is dimensionless and αn has dimension 1 − n.2 At last, the central quantity of this study, the conductivity, has dimension one, as guaranteed by the gauge invariance
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