Magnetothermopower of Nodal Line Semimetals

The search for materials with large thermopower is of great practical interest, e.g. for the design of thermocouples and thermoelectric generators. Dirac/Weyl semimetals under magnetic field have recently proven to exhibit superior thermoelectric properties, as compared to conventional metals and semiconductors. Unfortunately, in these materials, the thermopower is suppressed at low temperatures. Here, we study the thermoelectric properties of straight and circular nodal line semimetals, computing the Seebeck and Nernst coefficients for arbitrary temperature and magnetic field. Strikingly, when a sufficiently strong magnetic field is applied along the direction of the nodal line, the large degeneracy of states leads to a large, temperature-independent thermopower that grows in a non-saturating way with applied field. This result suggests a potential advantage of nodal line semimetals for low-temperature thermopower applications.