Unraveling the Topological Superconductivity of FeTeSe

Non-technical description: This project will answer fundamental questions about the properties of a new class of topological systems. The focus is on FeTeSe, where the novel state is believed to emerge from the combination of topology and superconductivity. This new direction in quantum materials promises an exploration of quantum properties. Nonetheless, it also raises an ongoing challenge in condensed matter, directly addressed by this proposal, how to uniquely identify the topological nature of emergent states. Proposed experiments will address this challenge directly by looking at the role of spin-orbit coupling, bandwidth, contact properties, symmetry, superconducting and topological order. The proposal includes informing K-12 about 2D materials and topology via the Lynch School of Education's Science Educators for Urban Schools program; talking directly to K-12 via the Skype a Scientist program; increasing participation of students in STEM by partnering with several programs. Technical description: Topological phases of matter, defined by an invariant in Hilbert space, are challenging to identify and probe. These are typically demonstrated via the bulk-boundary correspondence wherein the nontrivial topology produces new modes. For topological phases emerging in superconductors, the non-trivial nature of the boundary modes is challenging to reveal experimentally. These modes also hold the potential for future protected quantum bits in topological quantum computation. There is mounting evidence for such modes in the superconducting state of FeTeSe. This project builds on the principle investigator’s recent results suggesting a topological boundary mode in FeTeSe. To understand the relationship to the bulk order, systematic experiments will explore the device configurations and material parameters over which this occurs. In addition, the proposed experiments lend themselves to involving a diverse group of participants at the high school and undergraduate level in cutting-edge topics and techniques crucial to improving their representation in STEM. 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.