Planar Hall effect without external magnetic field in strained Weyl semimetals

The most intriguing property of a Weyl semimetal (WSM) is the chiral anomaly, i.e., the anomalous nonconservation of chiral current in the presence of external fields parallel to each other, which have been attracting intense experimental and theoretical interest. One of the fundamental manifestations of chiral anomaly in a WSM is the appearance of planar Hall effect (PHE), where an in-plane transverse voltage emerges in the presence of co-planar electric and magnetic fields. A natural quest, therefore, is whether there exists an alternate avenue to PHE, without invoking chiral anomaly. Using semiclassical Boltzmann transport theory, we show that PHE, remarkably, arises in a strained WSM even in the absence of the aforesaid anomaly and due to the strain-induced chiral gauge potential, which couples to the Weyl fermions of opposite chirality with opposite sign. Our study shows that strain causes a resultant phase shift in the current associated with opposite chirality Weyl nodes, which, interestingly, leads to a finite chirality-dependent planar Hall effect (CPHE) in the strained WSMs. We further show that a small tilt in the Weyl node can generate a pure CPHE even in the absence of an applied magnetic field. The CPHE has important implications in `chiralitytronics'. We also discuss the experimental feasibility of these novel effects in type-I strained WSMs.