Slater to Mott crossover in the metal to insulator transition of   Nd2Ir2O7
  We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd2Ir2O7 through its magnetic metal-insulator transition. Our data reveal that metallic Nd2Ir2O7 has a quadratic band, touching the Fermi level at the Gamma point, similarly to that of Pr2Ir2O7. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a non-dispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition. 
M. Nakayama, Takeshi Kondo, Z. Tian, J.J. Ishikawa, M. Halim, C.   Bareille, W. Malaeb, K. Kuroda, T. Tomita, S. Ideta, K. T...
cond-mat.str-el cond-mat.mtrl-sci