Nanoscale Imaging of Novel Electronic States in Kagome Metals

Non-technical Abstract: Materials can display unexpected behavior when atoms form special repeating patterns and when electrons interact strongly. This project examines a class of crystalline materials called kagome metals, whose atoms form hexagonal networks with corner-sharing triangles. These materials can host unusual electronic, magnetic, and superconducting phases that may help reveal principles useful for future electronic and quantum technologies. The research is important because it visualizes how these phases form and vary across a material at the scale of individual atoms, where many conventional measurements average over important local details. The project also integrates research with education by training graduate and undergraduate students in advanced materials measurement, data analysis, and scientific instrumentation. To support student engagement in physics and materials science, the principal investigator provides hands-on laboratory experiences for high school students through the Research Science Institute and supports laboratory tours and outreach talks for K-12 audiences. These activities provide early exposure to cutting-edge research and prepare students for careers in science and technology. Technical Abstract: This project addresses the microscopic origin, spatial organization, and local tunability of intertwined electronic and magnetic orders in kagome metals and superconductors. The scientific problem is to determine how kagome lattice geometry, electronic correlations, disorder, strain, and magnetic field produce electronic reconstruction, rotational symmetry breaking, density waves, superconductivity, and magnetic textures. The research focuses on two structural families of materials: A(V,Cr)3Sb5, where A is cesium, potassium, or rubidium, and CeTi3Bi4. Building on the principal investigator’s prior spectroscopic-imaging scanning tunneling microscopy discoveries in kagome superconductors and magnets, the research team uses variable-temperature spectroscopic-imaging scanning tunneling microscopy-based techniques with in situ vector magnetic field control to resolve electronic structure and magnetic response at atomic length scales. The project identifies local signatures of time-reversal symmetry breaking and possible orbital magnetic moments in AV3Sb5, determines how electronic rotational symmetry breaking and superconductivity evolve across the doping-driven phase diagram of AV3Sb5, images the nanoscale domain structure in CsCr3Sb5, and resolves spin-density-wave formation and its electronic consequences in CeTi3Bi4. By directly imaging symmetry breaking, domain formation, quasiparticle interference, and local electronic reconstruction in real space, the research establishes how geometry and correlations in kagome materials generate emergent quantum phases that are difficult to isolate with bulk-averaged probes. 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. NSF Award ID: 2615003 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Ilija Zeljkovic | Institution: Boston College, CHESTNUT HILL, MA | Award Amount: $429,939 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2615003 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2615003.html