Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 100: Electronic Structure of Surfaces II

O 100.1: Talk

Thursday, March 19, 2020, 10:30–10:45, REC C 213

Scanning tunneling spectroscopy on Be(0001) — •Hermann Osterhage, Roland Wiesendanger, and Stefan Krause — Department of Physics, University of Hamburg, Germany

Beryllium is an alkaline earth metal with peculiar electronic properties. The bulk material behaves similar to a semiconductor with a partial bandgap around the Fermi energy. In contrast, on the Be(0001) surface there is a delocalized electron system contributing substantially to the electronic density of states (DOS) at the Fermi energy.[1] Large amplitudes of Friedel oscillations seen in STM near the Fermi level disagree with a nearly free electron model.[2] A charge density wave and electron-phonon coupling were proposed as possible explanations for this deviation. More recently, the presence of Dirac node lines of surface bands in alkaline earth metals was identified as another possible cause for the unusually large amplitude observed in STM.[3]

While the surface bands of Be(0001) have been studied in angle resolved photoemission spectroscopy,[4] investigations using scanning tunneling spectroscopy have been lacking so far. We recorded tunneling spectra on a clean Be(0001) surface and mapped the charge oscillations at cryogenic temperatures. The energy dependence of the charge oscillations’ wave vector will be compared to the surface state dispersion derived from previous photoemission studies.

[1] P. J. Feibelmann et al., Phys. Rev. B 50, 17480 (1994).

[2] P. T. Sprunger et al., Science 275, 1764 (1997).

[3] R. Li et al., Phys. Rev. Lett. 117, 096401 (2016).

[4] K. B. Ray et al., Surf. Sci. 285, 66 (1993).