Valence characterisation of the subsurface region in

Abstract

Samarium hexaboride (), which lies in the mixed valence regime in the Anderson model, has been predicted to possess topologically protected surface states. The intensive investigations on 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 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 (1 0 0) 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.

Keywords:

• Mixed valence
• topological Kondo insulator
• photoemission
• strongly correlated electrons
• valence fluctuation
• samarium hexaboride
• surface effects

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Erratum

Acknowledgements

We would like to thank M. Kalläne, A. Quer, E. Kröger, Jens Viefhaus for assistance in using beamline P04. We also thank Diamond Light Source for access to beamline I09 (SI11952) and especially T.-L. Lee and C. Schlueter for experimental and technical support on site. C.H.M. is grateful for the helpful discussion with S. Suga.

Notes

No potential conflict of interest was reported by the authors.

This article was originally published with errors. This version has been updated. Please see Erratum (http://dx.doi.org/10.1080/14786435.2016.1201295) .

Additional information

Funding

This research was supported by the DFG [SFB 1170 ‘ToCoTronics’, projects C06, project RE 1469/8-1]; B.K.C. and B.Y.K. were supported by National Research Foundation of Korea (NRF) grants funded by the Korean government [MSIP, grant number 2011-0028736, Bank for Quantum Electronic Materials-BQEM00001]; Parts of this research were carried out at the light source PETRAIII at DESY, a member of the Helmholtz Association (HGF).