title: Nearly massless Dirac fermions hosted by Sb square net in BaMnSb2.
abstract: Layered compounds AMnBi2 (A = Ca, Sr, Ba, or rare earth element) have been established as Dirac materials. Dirac electrons generated by the two-dimensional (2D) Bi square net in these materials are normally massive due to the presence of a spin-orbital coupling (SOC) induced gap at Dirac nodes. Here we report that the Sb square net in an isostructural compound BaMnSb2 can host nearly massless Dirac fermions. We observed strong Shubnikov-de Haas (SdH) oscillations in this material. From the analyses of the SdH oscillations, we find key signatures of Dirac fermions, including light effective mass (~0.052m0; m0, mass of free electron), high quantum mobility (1280 cm(2)V(-1)S(-1)) and a π Berry phase accumulated along cyclotron orbit. Compared with AMnBi2, BaMnSb2 also exhibits much more significant quasi two-dimensional (2D) electronic structure, with the out-of-plane transport showing nonmetallic conduction below 120 K and the ratio of the out-of-plane and in-plane resistivity reaching ~670. Additionally, BaMnSb2 also exhibits a G-type antiferromagnetic order below 283 K. The combination of nearly massless Dirac fermions on quasi-2D planes with a magnetic order makes BaMnSb2 an intriguing platform for seeking novel exotic phenomena of massless Dirac electrons.
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70018, USA.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70018, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Hu
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, TN 37830, USA.
authors.forename: Huibo
authors.initials: H
authors.lastname: Cao
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70018, USA.
authors.forename: Yanglin
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70018, USA.
authors.forename: Alyssa
authors.initials: A
authors.lastname: Chuang
authors.affiliation: National High Magnetic Field Lab, Tallahassee, FL 32310, USA.
authors.forename: D
authors.initials: D
authors.lastname: Graf
authors.affiliation: Department of Physics and Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Adams
authors.affiliation: Department of Physics and Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148, USA.
authors.forename: S M A
authors.initials: SM
authors.lastname: Radmanesh
authors.affiliation: Department of Physics and Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148, USA.
authors.forename: L
authors.initials: L
authors.lastname: Spinu
authors.affiliation: National High Magnetic Field Lab, Tallahassee, FL 32310, USA.|Department of Physics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: I
authors.initials: I
authors.lastname: Chiorescu
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70018, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Mao