Enhanced Thermopower in Hole-doped Pyrochlore Iridates: Correlated Metal with Quadratic Band Touching

ORAL

Abstract

Quadratic band touching (QBT) is a band structure in which the parabolic valence and conduction band touch at a point, protected by spatial and time inversion symmetry. The possibility that QBT becomes the source of exotic electronic phases such as Weyl semimetal has been discussed. The existence of QBT has been confirmed in Pr2Ir2O7 (PIO), which is a member of pyrochlore-type iridate R2Ir2O7 (RIO, R=Rare earth). Since QBT in PIO is stabilized by the crystal symmetry, we can consider the possibility of the universal existence of QBT in the paramagnetic metallic phase of RIO. Therefore, we made hole-doped samples of insulator Eu2Ir2O7 to compare its electronic properties with PIO.
Using the charge transport measurement and ab-initio calculation, we have explored the thermopower and electronic structure of correlated metal with QBT in hole-doped pyrochlore iridates. We found that the hole-doped QBT yields a thermopower peak, which can be enhanced exceeding 40 V/K below 50 K by tuning the band-filling and lattice distortion. The thermopower peak is observed even in the doping induced metallic phase created from Mott insulator, indicating that the QBT is robust against the strong electron correlation as well as the lattice distortion while keeping the cubic symmetry.

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Presenters

  • Ryoma Kaneko

    Department of Applied Physics and Quantum-Phase Electronics Center, University of Tokyo, University of Tokyo

Authors

  • Ryoma Kaneko

    Department of Applied Physics and Quantum-Phase Electronics Center, University of Tokyo, University of Tokyo

  • Marie-Therese Philipp

    Center for Emergent Matter Science, RIKEN

  • Jun Fujioka

    Graduate School of Pure and Applied Sciences, University of Tsukuba, University of Tsukuba, University of Tokyo and JST-PRESTO

  • Shiro Sakai

    RIKEN, Center for Emergent Matter Science, RIKEN, University of Tokyo and RIKEN CEMS

  • Ryotaro Arita

    RIKEN, RIKEN Center for Emergent Matter Science, Department of Applied Physics and Quantum-Phase Electronics Center, University of Tokyo, University of Tokyo, University of Tokyo and RIKEN CEMS

  • Hiroshi Shinaoka

    Department of Physics, Saitama University

  • Kentaro Ueda

    Department of Applied Physics and Quantum-Phase Electronics Center, University of Tokyo, University of Tokyo

  • Yoshinori Tokura

    RIKEN Center for Emergent Matter Science (CEMS), RIKEN Center for Emergent Matter Science, RIKEN CEMS, RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan, Center for Emergent Matter Science (CEMS), RIKEN, Department of Applied Physics and Quantum-Phase Electronics Center, University of Tokyo, University of Tokyo, University of Tokyo and RIKEN CEMS, CEMS, RIKEN, Center for Emergent Matter Science, RIKEN, Department of Applied Physics, University of Tokyo, University of Tokyo and RIKEN-CEMS