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Proximity to Fermi-surface topological change in superconducting LaO0.54F0.46BiS2

Kensei Terashima, Junki Sonoyama, Takanori Wakita, Masanori Sunagawa, Kanta Ono, Hiroshi Kumigashira, Takayuki Muro, Masanori Nagao, Satoshi Watauchi, Isao Tanaka, Hiroyuki Okazaki, Yoshihiko Takano, Osuke Miura, Yoshikazu Mizuguchi, Hidetomo Usui, Katsuhiro Suzuki, Kazuhiko Kuroki, Yuji Muraoka, and Takayoshi Yokoya
Phys. Rev. B 90, 220512(R) – Published 22 December 2014
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    Abstract

    The electronic structure of nearly optimally doped novel superconductor LaO1−xFxBiS2(x=0.46) was investigated using angle-resolved photoemission spectroscopy (ARPES). We clearly observed band dispersions from 2 to 6 eV binding energy and near the Fermi level (EF), which are well reproduced by first-principles calculations when the spin-orbit coupling is taken into account. The ARPES intensity map near EF shows a squarelike distribution around the Γ(Z) point in addition to electronlike Fermi-surface (FS) sheets around the X(R) point, indicating that FS of LaO0.54F0.46BiS2 is in close proximity to the theoretically predicted topological change.

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    • Received 19 October 2014
    • Revised 2 December 2014

    DOI:https://doi.org/10.1103/PhysRevB.90.220512

    ©2014 American Physical Society

    Authors & Affiliations

    Kensei Terashima1,2, Junki Sonoyama1, Takanori Wakita1,2, Masanori Sunagawa1, Kanta Ono3, Hiroshi Kumigashira3, Takayuki Muro4, Masanori Nagao5, Satoshi Watauchi5, Isao Tanaka5, Hiroyuki Okazaki6,*, Yoshihiko Takano6, Osuke Miura7, Yoshikazu Mizuguchi7, Hidetomo Usui8, Katsuhiro Suzuki8, Kazuhiko Kuroki8, Yuji Muraoka1,2, and Takayoshi Yokoya1,2

    • 1Graduate School of Natural Science and Technology and Research Laboratory for Surface Science, Okayama University, Okayama 700-8530, Japan
    • 2Research Center of New Functional Materials for Energy Production, Storage, and Transport, Okayama University, Okayama 700-8530, Japan
    • 3High Energy Accelerator Research Organization (KEK), Photon Factory, Tsukuba, Ibaraki 305-0801, Japan
    • 4Japan Synchrtron Radiation Research Institute (JASRI)/SPring-8, Sayo, Hyogo 679-5198, Japan
    • 5Center for Crystal Science and Technology, University of Yamanashi, Kofu, Yamanashi 400-8511, Japan
    • 6National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
    • 7Department of Electrical and Electronic Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
    • 8Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan

    • *Present address: WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.

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    Issue

    Vol. 90, Iss. 22 — 1 December 2014

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    • Figure 1
      Figure 1

      Valence band energy distribution curves (a) of LaO0.54F0.46BiS2 taken along approximately the Γ(Z)−X(R) direction using photon energy of 70 eV, and their negative values of second derivatives [lower panel of (b)] as a function of binding energy and wave vector. Results of the band calculation for x=0.46 along the Γ-X direction is also plotted in the lower panel of (b) as dashed orange lines. The upper panel of (b) shows a Brillouin zone of LaO1−xFxBiS2 and calculated FS for x=0.46 (orange lines). The blue line corresponds to the measured momentum region.

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    • Figure 2
      Figure 2

      EDCs (a) and their second derivatives (b), and second derivatives of MDCs (c) in the vicinity of EF taken along the Γ(Z)−X(R) direction near the X(R) point. The thick line in (a) and green arrow (b) show the energy position of a broad hump. The inset of (b) shows the Brillouin zone and the measured momentum region (blue line).

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    • Figure 3
      Figure 3

      (a) ARPES intensity plot integrated over ±40meV with respect to EF as a function of two-dimensional wave vectors taken at hν=70eV, which is symmetrized according to the fourfold symmetry of the material. The original data is surrounded by gray dots. Red dashed lines denote Brillouin zone boundaries, and orange lines show calculated FS for x=0.46. The blue line shows the momentum cut of (c), while green lines show the measured momentum areas of (d). (b) is the same as (a) but taken with the use of hν=880eV light (±100meV with respect to EF). (c) and (d) EDCs and intensity plots as a function of wave vector and binding energy taken in momentum cuts shown in (a). The half-transparent gray line in (c) is a guide for the eye, and the half-transparent red lines in (d) are calculated bands at corresponding momenta.

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