Observation of a well-defined hybridization gap and in-gap states on the SmB6 (001) surface

Abstract

The rise of topology in condensed matter physics has generated strong interest in identifying novel quantum materials in which topological protection is driven by electronic correlations. Samarium hexaboride is a Kondo insulator for which it has been proposed that a band inversion between $5d$ and $4f$ bands gives rise to topologically protected surface states. However, unambiguous proof of the existence and topological nature of these surface states is still missing, and its low-energy electronic structure is still not fully established. Here we present a study of samarium hexaboride by ultra-low-temperature scanning tunneling microscopy and spectroscopy. We obtain clear atomically resolved topographic images of the sample surface. Our tunneling spectra reveal signatures of a hybridization gap with a size of about $8\mathrm{meV}$ and with a reduction of the differential conductance inside the gap by almost half, and surprisingly, several strong resonances below the Fermi level. The spatial variations of the energy of the resonances point towards a microscopic variation of the electronic states by the different surface terminations. High-resolution tunneling spectra acquired at $100\mathrm{mK}$ reveal a splitting of the Kondo resonance, possibly due to the crystal electric field.

arXiv comment9 pages, 7 figures

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Cited by in corpus (12)

• Magnetic and defect probes of the SmB${}_6$ surface state
• Orbital-selective Kondo-lattice and enigmatic f-electrons emerging from inside the antiferromagnetic phase of a heavy fermion
• Consistency between ARPES and STM measurements on SmB${}_6$
• Visualizing the atomic-scale origin of metallic behavior in Kondo insulators
• Definitive Surface Magnetotransport Study of SmB${}_6$
• Surface resonance of the (2$\times$1) reconstructed lanthanum hexaboride (001)-cleavage plane: a combined STM and DFT study
• Structural and electrical characterization of the monolayer Kondo-lattice compound CePt${}_6$/Pt(111)
• Comparative Scanning Tunneling Microscopy Study on Hexaborides
• An STM perspective on hexaborides: Surface states of the Kondo insulator SmB${}_6$
• Realizing a topological diode effect on the surface of a topological Kondo insulator
• Phase stability in SmB${}_6$
• Importance of orbital fluctuations for the magnetic dynamics in heavy-fermion compound SmB${}_6$