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A group of researchers led by TAKAYAMA Akari, Researcher, Tohoku University (currently Assistant Professor, Graduate School of Science, The University of Tokyo), TAKAHASHI Takashi (Professor, Graduate School of Science, The University of Tokyo) and SATO Takafumi (Associate Professor, Graduate School of Science, The University of Tokyo), and OGUCHI Tamio (Professor, The Institute of Scientific and Industrial Research, Osaka University) have discovered the Rashba effect takes place in Bi thin film with many edge structures, a world first.

To realize a one-dimensional (1D) system with strong spin-orbit coupling is a big challenge in modern physics, since the electrons in such a system are predicted to exhibit exotic properties unexpected from the 2D or 3D counterparts, while it was difficult to realize genuine physical properties inherent to the 1D system. We demonstrate the first experimental result that directly determines the purely 1D band structure by performing spin-resolved angle-resolved photoemission spectroscopy (spin-resolved ARPES) of Bi islands on a silicon surface that contains a metallic 1D edge structure with unexpectedly large Rashba-type spin-orbit coupling suggestive of the nontopological nature. We have also found a sizable out-of-plane spin polarization of the 1D edge state, consistent with our first-principles band calculations. Our result provides a new platform to realize exotic quantum phenomena at the 1D edge of the strong spin-orbit-coupling systems.


Figure 1.  Rashba effect at the semiconductor interface.

Figure 2.  Spin-resolved ARPES method.

Figure 3.  Schematic view of Bi thin film with the 1D edge state.

To learn more about this research, please view the full research report entitled "One-Dimensional Edge States with Giant Spin Splitting in a Bismuth Thin Film" at this page of the Physical Review Letters website.

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