Electron many-body effects in quantum point contacts

PhD ceremony: Mr. M.J. Iqbal, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Electron many-body effects in quantum point contacts

Promotor(s): prof. C.H. van der Wal

Facultty: Mathematics and Natural Sciences

How does electrical current flow in the smallest wires that can be realized? This PhD thesis presents experimental research that aimed at understanding this at a very fundamental level. The smallest wires that can be made are fabricated with nanotechnology, and have dimensions at the nanoscale. The width of such wires is at the scale of the quantum mechanical wavelength of electrons that flow in the wire, and this is not much larger than the scale of the individual atoms of the material that forms the wire. In such very small wires the electrical current behaves different than in wires that are larger (as the wires in our daily life). Electrons do not flow as individual electrons, but the electrical current depends on how a cloud of interacting electrons (electrons that feel each other’s presence) can flow in the wire. The work in this thesis discovered the underlying physics for this phenomenon, which was an important and highly debated open question in the field of nanoscience since 1996.

These studies were carried out under extreme conditions, where the electrical current shows most strongly how the interactions between electrons influence the electrical current. The wires were therefore made in extremely pure semiconductors, and studied at temperatures of less than 1 degree above absolute zero temperature (about 273 degrees Celsius below zero). The results are important for building the computers of the future.