Abstract
Dirac states hosted by Sb/Bi square nets are known to exist in the layered antiferromagnetic AMnX2 (A = CaSr/Ba/Eu/Yb, X=Sb/Bi) material family with the space group to be P4/nmm or I4/mmm. In this paper, we present a comprehensive study of quantum transport behaviors, angle-resolved photoemission spectroscopy (ARPES), and first-principles calculations on SrZnSb2, a nonmagnetic analog to AMnX2, which crystalizes in the pnma space group with distorted square nets. From the quantum oscillation measurements up to 35 T, three major frequencies including F1=103T, F2=127T, and F3=160T are identified. The effective masses of the quasiparticles associated with these frequencies are extracted, namely, m∗1=0.1 me, m∗2=0.1 me, and m∗3=0.09 me, where me is the free electron mass. From the three band Lifshitz-Kosevich fit, the Berry phases accumulated along the cyclotron orbit of the quasiparticles are 0.06π, 1.2π, and 0.74π for F1, F2, and F3, respectively. Combined with the ARPES data and the first-principles calculations, we reveal that F2 and F3 are associated with the two nontrivial Fermi pockets at the Brillouin zone edge while F1 is associated with the trivial Fermi pocket at the zone center. In addition, the first-principles calculations further suggest the existence of a Dirac nodal line in the band structure of SrZnSb2.
