Quantum materials with kagome lattice – comprised of corner-sharing triangles forming a hexagon in the crystal structure - have been studied as the potential playgrounds for exploring the interplay among parameters such as geometry, topology, electronic correlations, magnetic, and charge density orders. Niobium halides, Nb3X8 (X = Cl, Br, I), which are predicted to be two-dimensional magnets, have recently received attention due to their breathing kagome geometry. In this talk, I will discuss the electronic structure of Nb3X8 system revealed by angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations. ARPES results depict the presence of multiple flat and weakly dispersing bands. These bands are well reproduced by the theoretical calculations, which show that they have Nb d character indicating their origin from the Nb atoms forming the breathing kagome plane. These van der Waals materials can be easily thinned down via mechanical exfoliation to the ultrathin limit and such ultrathin samples are stable as shown from the time-dependent Raman spectroscopy measurements at room temperature. These results demonstrate that Nb3X8 system is an excellent material platform for studying breathing kagome induced flat band physics and its connection with magnetism. I will also discuss our recent results on topological quantum materials using ultrafast spectroscopy. 

About the speaker:

Dr. Neupane received his Ph.D. in Physics from Boston College, Boston, MA in 2010. He spent four years (2011-2014) as a postdoctoral research associate at Princeton University, Princeton, NJ and one year (2015-2016) as a Director’s Fellow at Los Alamos National Laboratory, Los Alamos, NM. He joined UCF in 2016 as an Assistant Professor and reached Associate Professor in 2020. He is the recipient of the Director’s Fellow at Los Alamos National Laboratory (2015), NSF Career Award (2019), UCF Luminary Award (2019), and UCF Research Incentive Award (2020). Neupane has been recognized as a highly cited researcher from 2019 to 2023 by analytics company Clarivate, based on data from Web of Science. His research focuses on the electronic and spin properties of new quantum materials. He utilizes various spectroscopic techniques to reveal the interesting electronic and spin properties as well as the momentum resolved dynamical properties of the bulk and symmetry-protected properties of the surface of these quantum materials.