Theory for Planar Hall Effect in Organic Dirac Fermion System

In a recent experiment on the interlayer magnetoresistance in the quasi-two-dimensional organic salt, α-(BEDT-TTF)2I3, it has been observed that at low temperatures, interlayer tunneling attains phase coherence, leading to the emergence of a three-dimensional electronic structure. Theoretically and experimentally it has been suggested that the system exhibits characteristics of a three-dimensional Dirac semimetal as a consequence of broken time-reversal symmetry and inversion symmetry. Here, we perform a theoretical calculation of the magnetoconductivity under an in-plane magnetic field and demonstrate that the system displays a planar Hall effect. Our calculations are based on a realistic model for α-(BEDT-TTF)2I3 incorporating interlayer tunneling and the tilt of the Dirac cone. Given that the planar Hall effect is anticipated as a consequence of chiral anomaly, our findings provide support for the classification of α-(BEDT-TTF)2I3 as a three-dimensional Dirac semimetal.