Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 22: Correlated Electrons: Low-dimensional Systems - Materials 1
TT 22.7: Vortrag
Mittwoch, 28. März 2012, 11:00–11:15, H 0104
Geometric frustration and competing phases of the Sn/Si(111) surface system — •Gang Li1, Philipp Höpfner2, Jörg Schäfer2, Ralph Claessen2, and Werner Hanke1 — 1Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany — 2Physikalisches Institut, Universität Würzburg, 97074 Würzburg, Germany
One third of a monolayer of Sn adatoms on the (111) surface of Si presents a quasi-two dimensional realization of a Mott-Hubbard system on an effective triangluar lattice, displaying an intricate interplay between lattice reconstructions, inherent (magnetical) frustration and emerging and competing low-T phases. We study the Sn/Si(111)-(√3×√3) adatom system with material specific many-body calculations and with angle-resolved photoelectron spectroscopy (ARPES). In a first step, we investigate the electronic correlation effects by combining the ab-initio density-functional approach with sophisticated many-body methods, i.e. DMFT, DCA, Dual Fermion and Variational Cluster methods. A metal-insulator transition with first (second) order at finite (zero) temperature is predicted, and the system is proven to be short-range correlated. The interplay of the electron-electron interaction and geometrical frustration favors a row-wise antiferromagnetic (RW-AFM) order. Comparing to ARPES, we find a good overall agreement between theory and experiment for the spectral function and its temperature dependence. In particular, the additional 3×3 symmetry observed in ARPES is explained as a spectral-weight redistribution corresponding to the RW-AFM.