Topological surface states interacting with bulk excitations in the Kondo insulator SmB${}_6$ revealed via planar tunneling spectroscopy

Abstract

Samarium hexaboride (SmB${}_6$), a well-known Kondo insulator in which the insulating bulk arises from strong electron correlations, has recently attracted great attention owing to increasing evidence for its topological nature, thereby harboring protected surface states. However, corroborative spectroscopic evidence is still lacking, unlike in the weakly correlated counterparts, including Bi${}_2$Se${}_3$. Here we report results from planar tunneling that unveil the detailed spectroscopic properties of SmB${}_6$. The tunneling conductance obtained on the (001) and (011) single crystal surfaces reveal linear density of states as expected for two and one Dirac cone(s), respectively. Quite remarkably, it is found that these topological states are not protected completely within the bulk hybridization gap. A phenomenological model of the tunneling process invoking interaction of the surface states with bulk excitations (spin excitons), as predicted by a recent theory, provides a consistent explanation for all of the observed features. Our spectroscopic study supports and explains the proposed picture of the incompletely protected surface states in this topological Kondo insulator SmB${}_6$.

arXiv comment17 pages, 3 figures, Supporting Information attached, accepted in Proc. Natl. Acad. Sci. USA

References in corpus (33)

• Topological Insulators
• Topological insulators and superconductors
• Topological Kondo Insulators
• Topological origin of subgap conductance in insulating bilayer graphene
• Two-dimensional Dirac fermions in a topological insulator: transport in the quantum limit
• Landau Quantization of Massless Dirac Fermions in Topological Insulator
• Surface electronic structure of the topological Kondo insulator candidate correlated electron system SmB6
• Low-temperature surface conduction in the Kondo insulator SmB${}_6$
• Correlated Topological Insulators with Mixed Valence
• Topological surface state in the Kondo Insulator Samarium Hexaboride
• Quantum oscillations in Kondo Insulator SmB${}_6$
• Observation of in-gap surface states in the Kondo insulator SmB6 by photoemission
• Unconventional Fermi surface in an insulating state
• Momentum-Resolved Landau-Level Spectroscopy of Dirac Surface State in Bi2Se3
• Direct observation of the spin texture in strongly correlated SmB6 as evidence of the topological Kondo insulator
• Cubic Topological Kondo Insulators
• Hybridization, Inter-Ion Correlation, and Surface States in the Kondo Insulator SmB6
• Polarity-driven surface metallicity in SmB${}_6$
• Tuning bulk and surface conduction in topological Kondo insulator SmB6
• Hybridization gap and Fano resonance in SmB${}_6$
• Electron Cotunneling into a Kondo Lattice
• Kondo Breakdown in Topological Kondo Insulators
• Emergence of a coherent in-gap state in SmB6 Kondo insulator revealed by scanning tunneling spectroscopy
• Momentum-Dependent Hybridization Gap and dispersive in-gap state of The Kondo Semiconductor SmB6
• Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6
• Correlation between bulk thermodynamic measurements and the low temperature resistance plateau in SmB6
• Quantum oscillations in topological superconductor candidate Cu${}_{0.25}$Bi${}_2$Se${}_3$
• The importance of Charge Fluctuations for the Topological Phase in SmB${}_6$
• Termination-dependent Surface In-gap States in a Mixed-valent Topological Insulator: SmB${}_6$
• Heavy surface state in a possible topological Kondo insulator: Magneto-thermoelectric transport on the (011)-plane of SmB${}_6$
• Surface state reconstruction in ion-damaged SmB_6
• Incomplete Protection of the Surface Weyl Cones of the Kondo Insulator SmB${}_6$: Spin Exciton Scattering
• Crossover of Magnetoresistance from Fourfold to Twofold Symmetry in SmB6 Single Crystal, a topological Kondo insulator

Cited by in corpus (28)

• Giant spontaneous Hall effect in a nonmagnetic Weyl-Kondo semimetal
• Anomalous 3D bulk AC conduction within the Kondo gap of SmB${}_6$ single crystals
• Majoranas in mixed-valence insulators
• Exciton topology and condensation in a model quantum spin Hall insulator
• Hall anomaly, Quantum Oscillations and Possible Lifshitz Transitions in Kondo Insulator YbB${}_{12}$: Evidence for Unconventional Charge Transport
• The Effects of Spin-Excitons on the Surface States of SmB6: A Photoemission Study
• Magnetic impurities in Kondo insulators: An application to samarium hexaboride
• Bulk Rotational Symmetry Breaking in Kondo Insulator SmB6
• Nonequilibrium Magnetic Oscillation with Cylindrical Vector Beams
• Planar tunneling spectroscopy of the topological Kondo insulator SmB${}_6$
• Quantum spin fluctuations in the bulk insulating state of pure and Fe-doped SmB6
• Puzzle maker in SmB6: accompany-type valence fluctuation state
• Ultrafast terahertz spectroscopy study of Kondo insulating thin film SmB${}_6$: evidence for an emergent surface state
• Fragility of the Kondo insulating gap against disorder: relevance to recent puzzles in topological Kondo insulators
• Spin-selective tunneling from nanowires of the candidate topological Kondo insulator SmB6
• Spectroscopic Evidence for the Direct Involvement of Local Moments in the Pairing Process of the Heavy-Fermion Superconductor CeCoIn${}_5$
• Universal properties of the near-gap spectra of SmB6: dynamical mean-field calculations and photoemission experiments
• How to identify and characterize strongly correlated topological semimetals
• Probing the interplay between surface and bulk states in the topological Kondo insulator SmB${}_6$ through conductance fluctuation spectroscopy
• An STM perspective on hexaborides: Surface states of the Kondo insulator SmB${}_6$
• Topological nature of the Kondo insulator SmB${}_6$ and its sensitiveness to Sm vacancy
• Realizing a topological diode effect on the surface of a topological Kondo insulator
• Highly tunable optics across a topological transition in organic polymers
• Hall coefficient diagnostics of surface state in pressurized SmB6
• Topological surface states in the Kondo insulator YbB${}_{12}$ revealed via planar tunneling spectroscopy
• Persistence of correlation-driven surface states in SmB6 under pressure
• Spatial interferences in the electron transport of heavy fermion materials
• Spectral properties of strongly correlated multi impurity models in the Kondo insulator regime: Emergent coherence, metallic surface states and quantum phase transitions