  Dirac and Weyl semimetals form an ideal platform for testing ideas developed
in high energy physics to describe massless relativistic particles. One such
quintessentially field-theoretic idea of chiral anomaly already resulted in the
prediction and subsequent observation of the pronounced negative
magnetoresistance in these novel materials for parallel electric and magnetic
fields. Here we predict that the chiral anomaly occurs - and has experimentally
observable consequences - when real electromagnetic fields E and B are replaced
by strain-induced pseudo-electromagnetic fields e and b. For example, a uniform
pseudomagnetic field b is generated when a Weyl semimetal nanowire is put under
torsion. In accord with the chiral anomaly equation we predict a negative
contribution to the wire resistance proportional to the square of the torsion
strength. Remarkably, left and right moving chiral modes are then spatially
segregated to the bulk and surface of the wire forming a "topological coaxial
cable". This produces hydrodynamic flow with potentially very long relaxation
time. Another effect we predict is the ultrasonic attenuation and
electromagnetic emission due to a time periodic mechanical deformation causing
pseudoelectric field e. These novel manifestations of the chiral anomaly are
most striking in the semimetals with a single pair of Weyl nodes but also occur
in Dirac semimetals such as Cd3As2 and Na3Bi and Weyl semimetals with unbroken
time reversal symmetry.
