Valence Characterization of Surface and Subsurface Region in SmB6

Abstract

Samarium hexaboride (SmB6), which lies in the mixed valence regime in the Anderson model, has been predicted to possess topologically protected surface states. The intensive investigations on SmB6 have brought up the long standing questions about the discrepancy between the surface and bulk electronic properties in rare-earth compounds in general. Here, we investigate and eventually clarify this discrepancy in the particular case of SmB6 by the photoemission core-level spectra. We focus on the change in both Sm and B states depending on time, temperature, probing depth, and surface termination on the cleaved (100) surface. Our spectra show that the unusual time-dependent change in the Sm valence occurs within a period of hours, which is not related to the adsorption of residual gases. Moreover, we observe a reduction of the surface feature in the B and Sm states on the same timescale accompanied by the formation of a subsurface region. Thus, it indicates the relatively slow charge redistribution between the surface and subsurface regions. Our findings demonstrate that the f states is strongly involved in the surface relaxation.

accepted in Phil. Mag

References in corpus (5)

• Direct observation of the spin texture in strongly correlated SmB6 as evidence of the topological Kondo insulator
• High Resolution Photoemission Study on Low-T_K Ce Systems: Kondo Resonance, Crystal Field Structures, and their Temperature Dependence
• Termination-dependent Surface In-gap States in a Mixed-valent Topological Insulator: SmB${}_6$
• Surface properties of SmB6 from x-ray photoelectron spectroscopy
• Optical conductivity of topological Kondo insulating states

Cited by in corpus (9)

• 4$f$ crystal field ground state of the strongly correlated topological insulator SmB${}_6$
• Bulk and surface electronic properties of SmB6: a hard x-ray photoelectron spectroscopy study
• Chemical and valence reconstruction at the surface of SmB6 revealed with resonant soft x-ray reflectometry
• Robust surface states and coherence phenomena in magnetically alloyed SmB6
• Irreversible proliferation of magnetic moments at cleaved surfaces of the topological Kondo insulator SmB6
• An STM perspective on hexaborides: Surface states of the Kondo insulator SmB${}_6$
• Phase stability in SmB${}_6$
• f-electron charge densities probed using core level non-resonant inelastic x-ray scattering
• Anomalous 4$f$ fine structure in TmSe${}_{1-x}$Te${}_x$ across the metal-insulator transition