Imaging the Kondo Insulating Gap on SmB6

Abstract

Topological insulators host spin-polarized surface states which robustly span the band gap and hold promise for novel applications. Recent theoretical predictions have suggested that topologically protected surface states may similarly span the hybridization gap in some strongly correlated heavy fermion materials, particularly SmB6. However, the process by which the Sm 4f electrons hybridize with the 5d electrons on the surface of SmB6, and the expected Fermi-level gap in the density of states out of which the predicted topological surface states must arise, have not been directly measured. We use scanning tunneling microscopy to conduct the first atomic resolution spectroscopic study of the cleaved surface of SmB6, and to reveal a robust hybridization gap which universally spans the Fermi level on four distinct surface morphologies despite shifts in the f band energy. Using a cotunneling model, we separate the density of states of the hybridized bands from which the predicted topological surface states must be disentangled. On all surfaces we observe residual spectral weight spanning the hybridization gap down to the lowest T, which is consistent with a topological surface state.

V2 update: added supplemental materials

References in corpus (1)

• Observation of in-gap surface states in the Kondo insulator SmB6 by photoemission

Cited by in corpus (13)

• Direct observation of the spin texture in strongly correlated SmB6 as evidence of the topological Kondo insulator
• Hybridization gap and Fano resonance in SmB${}_6$
• Observation of perfect Andreev reflection due to Klein paradox in a topological superconducting state
• Many-body Resonance in a Correlated Topological Kagome Antiferromagnet
• Consistency between ARPES and STM measurements on SmB${}_6$
• Surface and electronic structure of SmB${}_6$ through Scanning Tunneling Microscopy
• The Effects of Spin-Excitons on the Surface States of SmB6: A Photoemission Study
• Ultrafast terahertz spectroscopy study of Kondo insulating thin film SmB${}_6$: evidence for an emergent surface state
• Impurities or a neutral Fermi surface? A further examination of the low-energy ac optical conductivity of SmB${}_6$
• Surface vs bulk electronic structures of a moderately correlated topological insulator YbB6 revealed by ARPES
• Systematic manipulation of the surface conductivity of SmB${}_6$
• Ultrafast observation of electron hybridization and in-gap states formation in Kondo insulator SmB6
• f-electron charge densities probed using core level non-resonant inelastic x-ray scattering