Consistency between ARPES and STM measurements on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>SmB</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:math>
C. E. Matt, Harris Pirie, Anjan Soumyanarayanan, Y.-S. He, Michael M. Yee, Pengcheng Chen, Yu Liu, Daniel T. Larson, Wendel S. Paz, J. J. Palacios, Mohammad Hamidian, Jennifer E. Hoffman
Abstract
The Kondo insulator ${\mathrm{SmB}}_{6}$ has emerged as a primary candidate for exotic quantum phases, due to the predicted formation of strongly correlated, low-velocity topological surface states and corresponding high Fermi-level density of states. However, measurements of the surface-state velocity in ${\mathrm{SmB}}_{6}$ differ by orders of magnitude, depending on the experimental technique used. Here we reconcile two techniques, scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), by accounting for surface band bending on polar terminations. Using spatially resolved scanning tunneling spectroscopy, we measure a band shift of $\ensuremath{\sim}20$ meV between full-Sm and half-Sm terminations, in qualitative agreement with our density-functional theory calculations of the surface charge density. Furthermore, we reproduce the apparent high-velocity surface states reported by ARPES by simulating their observed spectral function as an equal-weight average over the two band-shifted domains that we image by STM. Our results highlight the necessity of local measurements to address inhomogeneously terminated surfaces or fabrication techniques to achieve uniform termination for meaningful large-area surface measurements of polar crystals such as ${\mathrm{SmB}}_{6}$.