Half-quantized planar thermal hall in spin-orbit coupled systems

An anomalous, approximately half-quantized "planar" thermal Hall effect has recently been observed and identified as a signature of chiral Majorana edge modes in the field-disordered state of the honeycomb magnet α-RuCl₃, a leading candidate for realizing a Kitaev quantum spin-liquid. Here, we demonstrate that a nearly half-quantized anomalous planar thermal Hall effect—where the applied magnetic field is in the same plane with the longitudinal and transverse heat currents—can also be observed at low temperatures in simple electron- and hole-doped semiconductors with generic spin-orbit couplings and trigonal warping. Our work shows that the half-quantized planar thermal Hall effect can emerge in non-topological systems and should not be viewed as definitive proof of the presence of chiral Majorana edge modes.