The properties of electron systems become increasingly exotic as one progresses from the three-dimensional (3D) case into lower dimensions. In 2D electron systems novel and intriguing physical phenomena, such as the integer and fractional quantum Hall effect, have been found. More recently, the realization of a single layer of graphite (graphene) has resulted in a wealth of unexpected and exciting physics. For instance, electron transport in graphene is governed by the relativistic Dirac equation rather than the Schrödinger equation. Similar excitement has been generated recently by the discovery of 2D topologically protected states displaying Dirac dispersion cones at the surface of bulk 3D insulators.
The predictions for 1D electron gases lead to even more exotic properties. There, the Fermi liquid approach breaks down spectacularly. It has been predicted that the 1D electron gas is much better described by the Luttinger liquid formalism, leading to many intriguing properties, among which the view that the electron loses its identity and separates into two collective excitations of the quantum mechanical many body system: a spinon that carries spin without charge, and a holon that carries the positive charge of a hole without its spin.
Within this project the intriguing physical properties of 1D wires on Ge(001) are investigated. We investigated the formation of Au, Pt, and Ir induced nanowires (see the pictures above) on Ge(001). We reported the observation of end-states in Pt atomic chains, electronically stabilized growth of iridium nanowires on Ge(001), the structural and electronic properties of Au induced nanowires on Ge(001) and the observation of a Peierls instability in atomic Pt chains.