Universal plateau in the thermoelectric Hall conductivity of Dirac/Weyl semimetals

The three-dimensional Dirac and Weyl semimetals can exhibit thermoelectric properties that are not possible in conventional metals and semiconductors. Here I focus in particular on the thermoelectric Hall effect, which is the generation of a transverse heat current upon applying an electric field in the presence of a magnetic field. I show, in particular, that the thermoelectric Hall conductivity acquires a robust plateau in the extreme quantum limit, and that the plateau value is independent of the field strength, disorder strength, carrier concentration, or carrier sign. I then discuss recent experiments on the three-dimensional Dirac semimetal ZrTe₅, which clearly exhibit this plateau. Other thermoelectric coefficients in the material, such as the thermopower and Nernst coefficient, are greatly enhanced over their zero-field values even at relatively low fields.