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Register a new userThe type II Weyl semimetals at low temperatures: chiral anomaly, elastic deformations, zero sound
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We consider the properties of the type II Weyl semimetals at low temperatures basing on the particular tight - binding model. In the presence of electric field directed along the line connecting the Weyl points of opposite chirality the occupied states flow along this axis giving rise to the creation of electron - hole pairs. The electrons belong to a vicinity of one of the two type II Weyl points while the holes belong to the vicinity of the other. This process may be considered as the manifestation of the chiral anomaly that exists without any external magnetic field. It may be observed experimentally through the measurement of conductivity. Next, we consider the modification of the theory in the presence of elastic deformations. In the domain of the considered model, where it describes the type I Weyl semimetals the elastic deformations lead to the appearance of emergent gravity. In the domain of the type II Weyl semimetals the form of the Fermi surface is changed due to the elastic deformations, and its fluctuations represent the special modes of the zero sound. We find that there is one - to one correspondence between them and the sound waves of the elasticity theory. Next, we discuss the influence of the elastic deformations on the conductivity. The particularly interesting case is when our model describes the intermediate state between the type I and the type II Weyl semimetal. Then without the elastic deformations there are the Fermi lines instead of the Fermi points/Fermi surface, while the DC conductivity vanishes. However, even small elastic deformations may lead to the appearance of large conductivity.
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We present a theory of magnetotransport phenomena related to the chiral anomaly in Weyl semimetals. We show that conductivity, thermal conductivity, thermoelectric and the sound absorption coefficients exhibit strong and anisotropic magnetic field dependences. We also discuss properties of magneto-plasmons and magneto-polaritons, whose existence is entirely determined by the chiral anomaly. Finally, we discuss the conditions of applicability of the quasi-classical description of electron transport phenomena related to the chiral anomaly.
After the experimental realization, the Berry curvature dipole (BCD) induced nonlinear Hall effect (NLHE) has attracted tremendous interest to the condensed matter community. Here, we investigate another family of Hall effect, namely, chiral anomaly induced nonlinear Hall effect (CNHE) in multi-Weyl semimetal (mWSM). In contrast to the BCD induced NLHE, CNHE appears because of the combination of both chiral anomaly and anomalous velocity due to non-trivial Berry curvature. Using the semiclassical Boltzmann theory within the relaxation time approximation, we show that, in contrast to the chiral anomaly induced linear Hall effect, the magnitude of CNHE decreases with the topological charge n. Interestingly, we find that unlike the case of n=1, the CNHE has different behaviors in different planes. Our prediction on the behavior of CNHE in mWSM can directly be checked in experiments.
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