Charge-neutral fermions and magnetic field-driven instability in insulating YbIr3Si7
Date
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Kondo lattice materials, where localized magnetic moments couple to itinerant electrons, provide a very rich backdrop for strong electron correlations. They are known to realize many exotic phenomena, with a dramatic example being recent observations of quantum oscillations and metallic thermal conduction in insulators, implying the emergence of enigmatic charge-neutral fermions. Here, we show that thermal conductivity and specific heat measurements in insulating YbIr3Si7 reveal emergent neutral excitations, whose properties are sensitively changed by a field-driven transition between two antiferromagnetic phases. In the low-field phase, a significant violation of the Wiedemann-Franz law demonstrates that YbIr3Si7 is a charge insulator but a thermal metal. In the high-field phase, thermal conductivity exhibits a sharp drop below 300 mK, indicating a transition from a thermal metal into an insulator/semimetal driven by the magnetic transition. These results suggest that spin degrees of freedom directly couple to the neutral fermions, whose emergent Fermi surface undergoes a field-driven instability at low temperatures.
Description
Advisor
Degree
Type
Keywords
Citation
Sato, Y., Suetsugu, S., Tominaga, T., et al.. "Charge-neutral fermions and magnetic field-driven instability in insulating YbIr3Si7." Nature Communications, 13, (2022) Springer Nature: https://doi.org/10.1038/s41467-021-27541-9.