Investigating Topology in Electronically Tailored Tetradymite Materials

Florida State University, Tallahassee FL

Investigators

Abstract

Non-Technical Abstract: Modern society thrives due to the development of thousands of specialized crystalline materials that are optimized to specific tasks. Many such materials, including those found in computers, cell phones, and satellites, were developed during the first “quantum revolution” when a radical new understanding of the atom was established. We are now in the midst of a second quantum revolution where even more novel features of the quantum world are poised to serve as the impetus for new functionalities in real materials. This award will support research into a specific sub-class of materials (called “tetradymites”) that have emerged with very interesting and unique properties. The goal of this project is to chemically alter these materials, and thereby identify the ingredients that are needed to optimize their unique properties and induce useful behavior. These materials can then be used to develop robust and unprecedented electronic devices for new technologies – including quantum computing. This project will also provide an energetic educational and training environment for undergraduates and graduate students, and postdoctoral researchers, with an emphasis on promoting full participation of underrepresented groups in science and technology fields. Researchers supported by the project will also promote the broader public interests by mentoring middle/high school students, presenting lectures and demonstrations at local K-12 schools and in public forums. Technical Abstract: For three dimensional topological materials, one of the most persistent challenges is to harvest their quantum properties in bulk specimens using mainstream probes. An important piece of this puzzle is that many useful properties do not emerge unless stringent criteria are met. At a minimum this includes, (i) that disorder induced impurity states are tightly controlled and (ii) that the Fermi energy is finely tuned to match the environs of their linearly dispersing electronic bands. For most real materials, these criteria are contradictory: how to robustly accomplish tuning (e.g., chemically) without introducing disorder? To attack these challenges, the PI will investigate chemical intercalation of the tetradymite materials Bi2(Se,Te)3, Sb2Te3 and (Ti,Zr,Hf)2Te2(P,As) to (i) control the position of the Fermi energy, (ii) control interactions between surface and bulk states, and (iii) induce superconductivity and other symmetry breaking ordering (e.g., to promote Majorana fermions). Across these series, standard probes will be used to monitor the intercalant distribution, the evolution of the electronic state, the Fermi surface topography, and the fingerprints of topological protection (e.g., Berry’s phase and anomalous Hall effect). This project will provide a robust and hands-on educational and training environment for undergraduates, graduate students, and postdoctoral researchers. The PI will also seek to promote participation of individuals from underrepresented groups. Researchers supported by the project will promote the broader public knowledge in STEM fields by mentoring middle/high school students, presenting lectures and demos at local K-12 schools and in public forums, and participating in community outreach events. 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.