Giant Rashba-type spin splitting in bulk BiTeI

Journal name:
Nature Materials
Year published:
Published online


There has been increasing interest in phenomena emerging from relativistic electrons in a solid, which have a potential impact on spintronics and magnetoelectrics. One example is the Rashba effect, which lifts the electron-spin degeneracy as a consequence of spin–orbit interaction under broken inversion symmetry. A high-energy-scale Rashba spin splitting is highly desirable for enhancing the coupling between electron spins and electricity relevant for spintronic functions. Here we describe the finding of a huge spin–orbit interaction effect in a polar semiconductor composed of heavy elements, BiTeI, where the bulk carriers are ruled by large Rashba-like spin splitting. The band splitting and its spin polarization obtained by spin- and angle-resolved photoemission spectroscopy are well in accord with relativistic first-principles calculations, confirming that the spin splitting is indeed derived from bulk atomic configurations. Together with the feasibility of carrier-doping control, the giant-Rashba semiconductor BiTeI possesses excellent potential for application to various spin-dependent electronic functions.

At a glance


  1. Basic properties of BiTeI.
    Figure 1: Basic properties of BiTeI.

    a, Crystal structure. b, Brillouin zone. c, Temperature-dependent electrical resistivity. d, Energy-band dispersions obtained by relativistic first-principles band calculation.

  2. Rashba-split conduction bands observed by ARPES (hν=21.2 eV).
    Figure 2: Rashba-split conduction bands observed by ARPES (hν=21.2 eV).

    a, Fermi-surface mapping overlaid on the two-dimensional Brillouin zone of BiTeI. b, Angle-integrated PES around the kII=0 region. The near- EF part is magnified (×30) to show the conduction-band structure. c, The ARPES image of the Rashba-split conduction bands. The right panels show the band contour images as functions of kx and ky at certain binding energies.

  3. Spin polarization of Rashba-split bands.
    Figure 3: Spin polarization of Rashba-split bands.

    a, Markers tracking the band dispersions overlaid on the ARPES intensity image. The markers show the peak positions of the EDCs and MDCs. Red (blue) markers represent the ‘spin-up’ ( ‘spin-down’) components, as confirmed by SRARPES shown in c,d. b, The Fermi-surface map. Green markers show the peak positions of MDCs at EF. The red line represents the momentum cut of the SRARPES images in c,d. c, The spin-polarization image obtained by SRARPES. d, The EDCs of SRARPES measured along kx . The red (blue) curves show the spin-up (spin-down) components. e, Calculated spin polarization on conduction-band dispersions along A–L (ky=0,kz=π/c). Only the -component is shown by the colour scale for comparison with the experiment. f, Calculated spin polarization overlaid on the Fermi surface at kz=π/c. The arrows show the orientation of spin whereas their colour indicates the degree of polarization.

  4. Subband structure of Rashba-split conduction band quantized in the band-bending accumulation layer.
    Figure 4: Subband structure of Rashba-split conduction band quantized in the band-bending accumulation layer.

    a, ARPES image along kx obtained by an hν=6.994 eV laser light source. The red markers show the peak positions of the EDC and MDC. The blue (green) curve is a guide for the eyes to trace the dispersions of the n=1 (n=2) subband. b, Calculated subband structures taking into account the quantization of the conduction band in the two-dimensional surface accumulation layer. c, The calculated potential energy as a function of the depth from the surface (z). d, The calculated electron density as a function of z.


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Author information


  1. Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan

    • K. Ishizaka,
    • M. Sakano,
    • T. Shimojima,
    • T. Sonobe,
    • R. Arita,
    • N. Nagaosa,
    • Y. Onose &
    • Y. Tokura
  2. Correlated Electron Research Group (CERG), RIKEN-ASI, Wako 351-0918, Japan

    • M. S. Bahramy,
    • R. Arita,
    • N. Nagaosa &
    • Y. Tokura
  3. Multiferroics Project, ERATO, JST, Tokyo 113-8656, Japan

    • H. Murakawa,
    • Y. Kaneko,
    • Y. Onose &
    • Y. Tokura
  4. Institute for Solid State Physics, University of Tokyo, Kashiwa, 277-8581, Japan

    • K. Koizumi &
    • S. Shin
  5. CREST, JST, Tokyo 102-0075, Japan

    • S. Shin
  6. Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan

    • H. Miyahara,
    • A. Kimura &
    • M. Taniguchi
  7. Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan

    • K. Miyamoto,
    • T. Okuda,
    • H. Namatame &
    • M. Taniguchi
  8. Condensed Matter Research Center, Institute of Materials Structure Science, KEK, Tsukuba, 305-0801, Japan

    • K. Kobayashi,
    • Y. Murakami &
    • R. Kumai
  9. National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan

    • R. Kumai


K.I., M.S., T. Shimojima and T. Sonobe carried out (SR)ARPES. K. Koizumi and S.S. shared the ARPES infrastructure at the Institute of Solid State Physics and assisted with measurements. H.M., A.K., K.M., T.O., H.N. and M.T. shared the SRARPES infrastructure at the Hiroshima Synchrotron Radiation Center and assisted with measurements. M.S.B., R.A. and N.N. carried out the calculations. K. Kobayashi, Y.M. and R.K. carried out X-ray diffraction and determined the crystal structure. H.M., Y.K. and Y.O. carried out the crystal growth and transport measurements. K.I. analysed the (SR)ARPES data and wrote the manuscript with input from M.S.B., H.M., R.A., N.N. and Y.T. Y.T. conceived and coordinated the project.

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