Background Information

Researchers are therefore trying to understand the physical properties of systems that are not as small as a single atom, but small enough that the physical properties can be dramatically different from those in a larger chunk of material. Mesoscopic systems display a variety of physical effects that have needed new or improved theoretical methods to describe them. For systems smaller than the inelastic scattering length, quantum size effects in small particles and quantum interference between strongly coupled particles give rise to new phenomena. The discrete electrostatic energy of a small system by the addition of a single electron governs the transport properties at low voltages, a phenomenon known as the Coulomb blockade effect. Quantum confinement creating low-dimensional systems leads to novel physics like the quantum Hall effect and fractional quantum Hall effect.

Quasi-two-dimensional systems, quantum wells, can be made from modulation doped semiconductor hetero-structures. Lower dimensional systems, quasi-one-dimensional quantum wires and quasi-zero-dimensional quantum dots, can be produced by electro-statically confining the electrons in the quantum wells or by etching techniques. The influence of the confinement, magnetic field and electron-electron interaction on the electronic properties of these systems have attracted a great attention. Thermodynamic properties and excitations of these systems can be studied.

The majority of the works have studied the excitations of the systems by transport and optical spectroscopy. Metals provide another set of materials where mesoscopic structures show interesting effects to study. Besides normal metal samples, superconductors do exhibit many properties which share the interest of several groups within this network. Josephson effects and their interplay with Coulomb blockade, quasiparticle phenomena and phenomena in superconductor-normal metal and superconductor-semiconductor interfaces and tunnel junctions, and even the mechanical properties of superconducting nanostructures will be studied.

Thermal properties of semiconductor, metal and insulating nanostructures have become a rather intensive topic of research also. Besides the fact that heat propagation and thermodynamic quantities in small structures are interesting as such because of the influence of the restricted size, these effects will be very important in designing new devices based on nanostructures.

Molecular electronics is the next phase in nanoelectronics. Progress in conventional "top-to-bottom" lithographic approach will fail, or at least slow down in not so long time, and the alternative will be its chemistry based "bottom-to-top" counterpart, where electronic circuits will be built starting from molecules of proper electrical characteristics. Many groups in this network investigate carbon nanotubes, which represent one of the most promising examples of the present day "molecular electronic" building blocks.