Electrical and Magnetic Properties of PdSb₂ and PtBi₂ with Multiple Band Degeneracy

The discovery of topological properties in condensed matter started a new era of physics. Many fermionic particles and phenomena predicted in high energy physics are now experimentally observed in topological materials such as Dirac, Weyl, and Majorana particles. Their nontrivial topology results from crossings of conduction and valence bands. Depending on crystal symmetry, such crossings can result in degeneracy (g) with g = 2, 3, 4, 6, and 8. It is known that g = 2 corresponds to Weyl fermions, and g = 4 corresponds to Dirac fermions. The cases of g = 3, 6, and 8 are of particularly interesting as they can only be found in condensed matter systems, having no high energy analogues as constrained by Poincare symmetry. In this talk, I will present our experimental investigations on a 4d compound PdSb₂ with g = 6, and a 5d compound PtBi₂ with g = 3. By analyzing both the de Haas-van Alphen and Shubnikov-de Haas oscillations observed in these compounds, we obtain topological properties of the bands. The implications of these findings will be discussed.