Thermoelectric quantum oscillations and Zeeman splitting in topological Dirac semimetal BaAl4

Abstract

Three-dimensional topological semimetals hosting Dirac or Weyl fermions are a new kind of materials class in which conduction and valence bands cross each other. Such materials harbor a nontrivial Berry phase, which is an additional geometrical phase factor arising along the path of an adiabatic surface and can give rise to experimentally measurable quantities such as an anomalous Hall component. Here we report a systematic study of quantum oscillations of thermoelectric power in single crystals of the topological Dirac nodal-line semimetal BaAl₄. We show that the thermoelectric power (TEP) is a sensitive probe of the multiple oscillation frequencies in this material, with two of these frequencies shown to originate from the three-dimensional Dirac band. The detected Berry phase provides evidence of the angular dependence and non-trivial state under high magnetic fields. We also have probed the signatures of Zeeman splitting, from which we have extracted the Landé $g$-factor for this system, providing further insight into the non-trivial topology of this family of materials.