Quantum oscillation studies of the Dirac fermions hosted by distorted Sb square net in SrZnSb$_2$ single crystals.

Dirac states hosted by Sb/Bi square nets are known to exist in the layered antiferromagnetic AMnX$_2$ (A = Ca/Sr/Ba/Eu/Yb, X=Sb/Bi) material family. In this paper, we present high field quantum oscillation studies on SrZnSb$_2$, a nonmagnetic analogue to AMnX$_2$, and show the nontrivial Berry phase accumulation and light effective masses of the quasiparticles in this system. These results are in good agreement with the predicted topological state in SrZnSb$_2$. The angular dependence of the de Haas van Alphen oscillations further reveals that the Fermi surfaces are quasi 2D-like, similar to those in the AMnX$_2$ materials.