Seminars Archive

Quantum size effects and topological insulators.

Abstract
A key aspect of quantum mechanics is that when an electron is trapped in a small region of space its wave-like properties lead to quantization i.e. the electron can only occupy one of a limited number of well-defined allowed states. In the simple case of a particle in a box the allowed electron wavelengths are determined by the size of the box, in the same way that the notes of a guitar string are determined by the length of the string. I will describe a system in which the converse is observed i.e. the wavelength of the electrons in a particular material (Bismuth) governs the size of the nanostructures that can be formed. This is a novel “quantum size effect” where the widths of the nanostructures are quantised. This is analogous to a string that adjusts its own length in order to match a selected a musical note! I will describe how the quantum size effects were observed (using a Scanning Tunneling Microscope) and, on the way, review some other aspects of my group’s research into self-assembly of nanostructures. I will conclude by suggesting that the bismuth nanostructures are an ideal model system for exploring the interplay of quantum and topological effects – Topological Insulators are currently one of the hottest topics in physics because of the wealth of novel fundamental phenomena and potential applications in spintronics, quantum computation etc.