Surface valence transition in SmS by alkali metal adsorption

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.

7 pages, 6 figures

References in corpus (6)

• Quantum Criticality in Heavy Fermion Metals
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• Observation of an electron band above the Fermi level in FeTe${}_{0.55}$Se${}_{0.45}$ from \emph{in-situ} surface doping
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Cited by in corpus (2)

• Current-Induced Metallization and Valence Transition in Black SmS
• Photo-induced phase transition on black samarium monosulfide