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Project E1: Electronic properties of noble metal nanowires on stepped templates

Jörg Schäfer, Ralph Claessen

This project focusses on the electronic properties of quasi-one-dimensional (quasi-1D) nanowires grown by self-organization on terraced semiconductor surfaces. The central model systems are the chains induced by Au and Pt on Si(553) and Si(557). The physics in these systems is characterized by instabilities as a function of temperature, leading to superstructures and a metal-insulator-transition in selected electron bands. The atomic and electronic properties of these structures are accessible by scanning tunneling microscopy (STM) and spectroscopy (STS), which is complemented by angle-resolved photoemission (ARPES), all of which is performed down to low temperatures. The model systems allow to vary the interaction parameters by use of different high-index crystal surfaces or adatom species, and, importantly, the band-filling of these nanowires can be altered effectively by external doping. We will address the complex interplay between lattice, charge, and spin degrees of freedom, which includes the role of nesting conditions for an instability in the presence of strong spin-orbit coupling, the resulting energy gaps, as well as the existence of fluctuations that mask the phase transition. Special emphasis will thus be given to high-resolution studies of the many-body spectral function on the low-energy scale. The many-body signatures addressed here provide complementary data to those those from optical spectroscopy, electron loss and time-resolved measurements, and will provide important input for the modeling in the theory projects.

(Picture: High resolution STM picture of atomically resolved Au-chain structures grown on Ge(100).)