title: Quadratic Fermi node in a 3D strongly correlated semimetal.
abstract: Strong spin-orbit coupling fosters exotic electronic states such as topological insulators and superconductors, but the combination of strong spin-orbit and strong electron-electron interactions is just beginning to be understood. Central to this emerging area are the 5d transition metal iridium oxides. Here, in the pyrochlore iridate Pr2Ir2O7, we identify a non-trivial state with a single-point Fermi node protected by cubic and time-reversal symmetries, using a combination of angle-resolved photoemission spectroscopy and first-principles calculations. Owing to its quadratic dispersion, the unique coincidence of four degenerate states at the Fermi energy, and strong Coulomb interactions, non-Fermi liquid behaviour is predicted, for which we observe some evidence. Our discovery implies that Pr2Ir2O7 is a parent state that can be manipulated to produce other strongly correlated topological phases, such as topological Mott insulator, Weyl semimetal, and quantum spin and anomalous Hall states.
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kondo
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakayama
authors.affiliation: Physics Department, University of California, Santa Barbara, California 93106, USA.|Physics Department, University of California, Berkeley, California 94720, USA.|Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: R
authors.initials: R
authors.lastname: Chen
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: J J
authors.initials: JJ
authors.lastname: Ishikawa
authors.affiliation: Physics Department, University of California, Santa Barbara, California 93106, USA.|Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
authors.forename: E-G
authors.initials: EG
authors.lastname: Moon
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ota
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.|Physics Department, Faculty of Science, Beirut Arab University, P. O. Box 11-5020 Beirut, Lebanon.
authors.forename: W
authors.initials: W
authors.lastname: Malaeb
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kanai
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakashima
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ishida
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Yoshida
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.|Energy Materials Laboratory, Toyota Technological Institute, Nagoya 468-8511, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Matsunami
authors.affiliation: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.|Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kimura
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Inami
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ono
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kumigashira
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.|PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Nakatsuji
authors.affiliation: Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA.
authors.forename: L
authors.initials: L
authors.lastname: Balents
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Shin