title: Evidence of Topological Nodal-Line Fermions in ZrSiSe and ZrSiTe.
abstract: A Dirac nodal-line semimetal phase, which represents a new quantum state of topological materials, has been experimentally realized only in a few systems, including PbTaSe_{2}, PtSn_{4}, and ZrSiS. In this Letter, we report evidence of nodal-line fermions in ZrSiSe and ZrSiTe probed in de Haas-van Alphen quantum oscillations. Although ZrSiSe and ZrSiTe share a similar layered structure with ZrSiS, our studies show the Fermi surface (FS) enclosing a Dirac nodal line has a 2D character in ZrSiTe, in contrast with 3D-like FS in ZrSiSe and ZrSiS. Another important property revealed in our experiment is that the nodal-line fermion density in this family of materials (∼10^{20}  cm^{-3}) is much higher than the Dirac fermion density of other topological materials with discrete nodes. In addition, we have demonstrated ZrSiSe and ZrSiTe single crystals can be thinned down to 2D atomic thin layers through microexfoliation, which offers the first platform to explore exotic properties of topological nodal-line fermions in low dimensions.
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Tang
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Xue
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Yanglin
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: National High Magnetic Field Lab, Tallahassee, Florida 32310, USA.
authors.forename: David
authors.initials: D
authors.lastname: Graf
authors.affiliation: Department of Physics, University of California, Riverside, California 92521, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Myhro
authors.affiliation: Department of Physics, University of California, Riverside, California 92521, USA.
authors.forename: Son
authors.initials: S
authors.lastname: Tran
authors.affiliation: Department of Physics, University of California, Riverside, California 92521, USA.
authors.forename: Chun Ning
authors.initials: CN
authors.lastname: Lau
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Jiang
authors.initials: J
authors.lastname: Wei
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Mao