Alpha tin (α), also known as gray tin, is a particular crystalline phase of ordinary tin which, under appropriate conditions, may exhibit extraordinary electronic properties. For example, the mechanical compression exerted by the lattice of specific substrates stabilizes the electron structure of a topological Dirac semimetal, similar to the one observed in graphene. This unusual quantum phase of matter is characterized by intriguing properties. It allows electrons to move with high mobility, making α-tin an ideal candidate for spintronic applications and for the development of advanced and efficient nanoelectronic devices.
In this context, an international research team, including Carolina Crosta and Fabio Pezzoli, scientists of the Department of Materials Science at the University of Milano-Bicocca, has recently published an innovative study on the prestigious journal Matter [Cell Press, Impact Factor 18.4, 2023 (Clarivate Analytics), https://www.sciencedirect.com/science/article/pii/S2590238525002371]. The research explores how quantum confinement allows a precise modulation of the topological phase of tin, thus opening new application perspectives.
The study focuses on thin films of α-tin epitaxially grown on InSb(111) substrates. Sophisticated experimental techniques, such as transport and magneto-absorption, enabled researchers to observe phenomena that occur by reducing the thickness of the films and eventually affect fundamental properties such as effective mass and conductivity. These results show that α-tin is a fascinating material, which combines the simplicity of a pure element with the complexity of advanced quantum behaviour, thus opening new frontiers in research and technological applications.