Magnetic order mediated by fluctuating valence bonds in a quasi-2D quantum magnet Cu3B2O6
Feb 4, 2022
2:30PM to 3:30PM
Date(s) - 04/02/2022
2:30 pm - 3:30 pm
In condensed matter physics, “interaction” typically refers to the interaction between the same type of (quasi)-particles, such as electron-electron or magnon-magnon interaction. A system in which two different species of magnetic quasi-particles can interact has not been explored much due to the difficulty of finding a suitable experimental system. In this talk, we will discuss just such an example, Cu3B2O6, a quasi-two-dimensional quantum magnet. In our neutron scattering investigation, we found magnetic Bragg peaks with ordering wavevector of q=(0.5, 0, 0) below 10 K as well as a magnon mode emanating from the magnetic wavevector. Surprisingly, additional high-energy excitations are observed that show a distinct ring-like momentum dependence and a very weak energy dependence, which can be modelled using fluctuating valence bonds. Taken together, our findings suggest that Cu3B2O6 harbours a novel magnetic ground state where only a fraction of Cu spins participate in magnetic order, and the rest form spin-singlets with their neighboring spins. Moreover, the fluctuation of such singlets, or triplons, seems to be interacting with the magnons in this system.
Young-June Kim is a Professor of Physics at the University of Toronto. He received his Ph. D. degree from Harvard University in 1999 and carried out postdoctoral research at Massachusetts Institute of Technology and Brookhaven National Laboratory. In 2004, he joined the University of Toronto as an Assistant Professor and Canada Research Chair (Tier 2) in complex materials. His research centres around synthesizing novel quantum materials and studying their physical properties using advanced x-ray and neutron spectroscopy methods. In particular, he played a major role in developing resonant inelastic x-ray scattering (RIXS) and its application to study a wide range of quantum condensed matter systems, such as quantum spin liquids, superconductors, and thermoelectric materials. He has published more than 140 peer-reviewed articles and has given more than 100 invited talks and seminars. He is a Fellow of the American Physical Society, a member of the editorial board of Journal of Physics: Condensed Matter. He has also served on many advisory and review committees at large scientific facilities such as Advanced Photon Source and Stanford SLAC laboratory and is currently a Chair of the Molecular & Materials Science Experiments Evaluation Committee at TRIUMF. He also served as the director of the HEATER Program, a multi-institutional research and training program in thermoelectric materials.