**Exotic phenomena in Dirac and Weyl semimetals**

Dirac and Weyl semimetals contain electrons that behave in many respects as massless relativistic particles. They exhibit a variety of exotic behaviors including the so called chiral anomaly predicted more than 40 years ago in the context of high energy physics. The anomaly occurs when both electric and magnetic fields are applied to the material and has measurable consequences for the electric transport. This has already been observed in several candidate Dirac and Weyl semimetals. Using a combination of analytical tools and numerical techniques we predicted that, remarkably, the chiral anomaly can occur in Dirac and Weyl semimetals when real EM fields are replaced by strain-induced pseudo-EM fields [1]. Similar effect has been previously reported in graphene, a quintessential two-dimensional material with Dirac fermions. Such strain-induced pseudomagnetic field can be quite large (estimated up to 15T under reasonable strain in Cd_{3}As_{2}) and can result in quantum oscillations in complete absence of the applied magnetic field [2].

The goal of the project is to further explore the physics of strain-induced fields in three-dimensional Dirac and Weyl semimetals theoretically and establish the existence of the above mentioned phenomena experimentally. This will require developing quantitative theoretical predictions in close collaboration with experimentalists who will then attempt experimental detection. The theory predicts some remarkable novel effects such as the concept of topological coaxial cable with hydrodynamic flow of electrons as well as a unique coupling between electrons and phonons Dirac and Weyl semimetals. Some of these effects could have technological applications.

## References

[1] D.I. Pikulin, Anffany Chen, and M. Franz, "Chiral anomaly from strain-induced gauge fields in Dirac and Weyl semimetals " arXiv:1607.01810

[2] Tianyu Liu, D. I. Pikulin, M. Franz, "Quantum oscillations without magnetic field" arXiv:1608.04678

## Principal investigators

M. Franz (UBC),

D.A. Bonn (UBC)

W.N. Hardy (UBC),

C. Felser (MPI Dresden)