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Topological state in Kondo insulators has been provoked in SmB6, but the origin of surface states and topological order remain elusive. Here, Hagiwara et al. report temperature dependent reconstruction of a metallic surface state on the (001) surface of YbB12driven by Kondo effect and discuss its origin from topology.

Vicinal surfaces exhibiting arrays of atomic steps are frequently investigated due to their diverse physical-chemical properties and their use as growth templates. However, surfaces featuring steps with a large number of low-coordinated kink-atoms have been widely ignored, despite their higher potential for chemistry and catalysis. Here, the equilibrium structure and the electronic states of vicinal Ag(111) surfaces with densely kinked steps are investigated in a systematic way using a curved crystal. With scanning tunneling microscopy we observe an exceptional structural homogeneity of this class of vicinals, reflected in the smooth probability distribution of terrace sizes at all vicinal angles. This allows us to observe, first, a subtle evolution of the terrace-size distribution as a function of the terrace-width that challenges statistical models of step lattices, and second, lattice fluctuations around resonant modes of surface states. As shown in angle resolved photoemission experiments, surface states undergo stronger scattering by fully-kinked step-edges, which triggers the full depletion of the two-dimensional band at surfaces with relatively small vicinal angles.

Theelectric field control of functional properties is a crucial goalin oxide-based electronics. Nonvolatile switching between differentresistivity or magnetic states in an oxide channel can be achievedthrough charge accumulation or depletion from an adjacent ferroelectric.However, the way in which charge distributes near the interface betweenthe ferroelectric and the oxide remains poorly known, which limitsour understanding of such switching effects. Here, we use a first-of-a-kindcombination of scanning transmission electron microscopy with electronenergy loss spectroscopy, near-total-reflection hard X-ray photoemissionspectroscopy, and ab initio theory to address this issue. We achievea direct, quantitative, atomic-scale characterization of the polarization-inducedcharge density changes at the interface between the ferroelectricBiFeO3and the doped Mott insulator Ca1–xCexMnO3, thusproviding insight on how interface-engineering can enhance these switchingeffects. [ABSTRACT FROM AUTHOR]