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arXiv · 2205.15522

Surface valence transition in SmS by alkali metal adsorption

Takuto Nakamura·Toru Nakaya·Yoshiyuki Ohtsubo·Hiroki Sugihara·Kiyohisa Tanaka·Ryu Yukawa·Miho Kitamura·Hiroshi Kumigashira·Keiichiro Imura·Hiroyuki S. Suzuki·Noriaki K. Sato·Shin-ichi Kimura
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Abstract

The electronic structure changes of SmS surfaces under potassium (K) doping are elucidated using synchrotron-based core-level photoelectron spectroscopy and angle-resolved photoelectron spectroscopy (ARPES). The Sm core-level and ARPES spectra indicate that the Sm mean valence of the surface increased from the nearly divalent to trivalent states, with increasing K deposition. Carrier-induced valence transition (CIVT) from Sm$^{2+}$ to Sm$^{3+}$ exhibits a behavior opposite to that under conventional electron doping. Excess electrons are trapped by isolated excitons, which is inconsistent with the phase transition from the black insulator with Sm$^{2+}$ to the gold metal with Sm$^{3+}$ under pressure. This CIVT helps to clarify the pressure-induced black-to-golden phase transition in this material, which originates from the Mott transition of excitons.

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Takuto Nakamura, Toru Nakaya, Yoshiyuki Ohtsubo, Hiroki Sugihara, Kiyohisa Tanaka, Ryu Yukawa, Miho Kitamura, Hiroshi Kumigashira, Keiichiro Imura, Hiroyuki S. Suzuki, Noriaki K. Sato, Shin-ichi Kimura. 2022-05-31. Surface valence transition in SmS by alkali metal adsorption. https://doi.org/10.1103/physrevb.107.l041102

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