Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 58: Poster Session III (Solid-liquid interfaces; Scanning probe and other methods; Electronic structure theory; Spin-orbit interaction)

O 58.16: Poster

Mittwoch, 13. März 2013, 18:15–21:45, Poster B1

Scanning tunneling spectroscopy of the highly correlated electron system Sn on Si(111) — •Jochen Settelein¹, Philipp Höpfner¹, Jörg Schäfer¹, Gang Li², Werner Hanke², and Ralph Claessen¹ — ¹Physikalisches Institut, Universität Würzburg — ²Inst. für Theoret. Physik und Astronomie, Universität Würzburg

Two-dimensional electron systems can be realized at the surface of semiconductors by metal atom adsorption. A particularly intriguing scenario emerges for submonolayer coverages, since strong electron correlations come into play. At the same time, if a triangular lattice symmetry is chosen, any concomitant spin order faces the problem of geometric frustration. Here we address these intriguing questions by studying the reconstruction of Sn on Si(111) which, contrary to naive expectation of a metallic state, is suggestive of a Mott-Hubbard insulator at low temperatures [1].

We have studied the electronic properties by scanning tunneling microscopy and spectroscopy (STS). The tunneling spectra at low temperature show a characteristic dip around the Fermi level, indicative of insulating behavior. The spectral features on either side can well be interpreted in terms of lower and upper Hubbard band, respectively. Above 40 K the differential conductivity at the Fermi level increases gradually. The results are consistent with advanced many-body modeling by a dynamical cluster approximation. The STS results support the view as Mott insulator without a sharp transition as a function of temperature, and point at the role of longer-ranged correlations.

[1] S. Modesti et al., Phys. Rev. Lett. 98, 126401 (2007).