Non-trivial Berry Phase and strong Zeeman splitting in Topological Dirac semimetal BaAl₄ probed by thermoelectric quantum oscillations

Three-dimensional topological Dirac semimetals hosting Dirac/Weyl fermions are a new kind of Dirac materials in which conduction and valence bands cross each other. Quantum oscillation measurement is an important technique to extract the relativistic natures of Dirac fermions in topological quantum materials. Topological materials exhibit nontrivial Berry phase which also can be determined by the analysis of quantum oscillations. Here we report systematic study of thermoelectric power quantum oscillation of recently discovered topological Dirac nodal-line semimetal BaAl₄ single-crystal. We have shown that the thermoelectric power is a sensitive probe to study multiple quantum oscillations where two of these oscillations are shown to originate from three-dimensional Dirac band. The detected Berry phase develops an evidence of 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.