CAREER: Advanced Phase Control of Single-Elemental Films and Heterostructures

Non-technical Abstract: Elemental tin (Sn) presents a rare opportunity to explore quantum phenomena using a clean, single element platform. In its two distinct structural forms—alpha-Sn with topological properties and beta-Sn as a conventional superconductor—Sn offers a natural setting to study the interplay between topology and superconductivity. However, existing synthesis techniques often produce mixed-phase films, limiting both fundamental discovery and future applications in quantum technology. This project seeks to overcome those limitations by developing precise, scalable methods to selectively grow phase-pure Sn films and construct heterostructures with atomically sharp interfaces between topological and superconducting regions. The research is closely integrated with educational goals that include using these high-quality materials in undergraduate laboratories and outreach demonstrations. These efforts aim to inspire a new generation of scientists by making cutting-edge quantum materials research accessible and engaging to students from all backgrounds and educational levels. Technical Abstract: This research focuses on understanding and controlling the structural phase formation in epitaxial Sn films by tuning lattice strain and film thickness. The principal investigator hypothesizes that such control enables the selective growth of alpha-Sn and beta-Sn phases, allowing the creation of single-elemental heterostructures with clean interfaces. The project includes four interrelated thrusts: (1) synthesizing phase-pure Sn films by strain engineering, (2) uncovering their intrinsic quantum properties such as Luttinger semimetal behavior and superconductivity, (3) constructing alpha-Sn/beta-Sn junctions through engineered lattice transitions, and (4) probing emergent quantum phenomena in Sn-based Josephson junctions to reveal the interplay between topology and superconductivity. The research builds on preliminary results and leverages state-of-the-art molecular beam epitaxy and transport measurement techniques. Educational activities are interwoven with the research plan, using the developed materials and devices in classroom experiments and public outreach. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.