SPECIAL SEMINAR: Quantum transport of Dirac fermions in BaMnSb2 and SrZnSb2

 

 

Dirac states hosted by Sb/Bi square nets are known to exist in the layered antiferromagnetic AMnX2(A = Ca/Sr/Ba/Eu/Yb, X=Sb/Bi) material family. These materials share common structure characteristics, consisting of alternately stacked MnX4 tetrahedral layers and A-X-A sandwich layers. Among them, BaMnSb2has the highest resistivity anisotropy (rzz/rxx~1000 at 2K) and displays quantum oscillations with the smallest single frequency (F~ 20T). In this talk, I will first present our results from the quantum transport measurement on BaMnSb2under pulsed magnetic fields. We have observed a bulk half-integer quantum Hall effect accompanied by a 2D chiral metal state at the surface in the extreme quantum limit in BaMnSb2. In the second part of the talk, I will briefly show our magneto-transport and electronic structure studies on a nonmagnetic analogue, SrZnSb2. With the replacement of Mn by Zn, Dirac fermions still exist in the system while carriers from trivial bands also contribute to the transport. Interestingly, the first-principles calculations suggest the formation of a Dirac node line in the band structure of SrZnSb2. We believe the 112 layered material family can serve as an intriguing platform for seeking novel exotic phenomena of quasi 2D Dirac electrons.