Charge-neutral fermions and magnetic field-driven instability in insulating YbIr3Si7

Y. Sato, S. Suetsugu, T. Tominaga, Y. Kasahara, S. Kasahara, T. Kobayashi, S. Kitagawa, K. Ishida, R. Peters, T. Shibauchi, A. H. Nevidomskyy, L. Qian, E. Morosan and Y. Matsuda ()
Additional contact information
Y. Sato: Kyoto University
S. Suetsugu: Kyoto University
T. Tominaga: Kyoto University
Y. Kasahara: Kyoto University
S. Kasahara: Kyoto University
T. Kobayashi: Kyoto University
S. Kitagawa: Kyoto University
K. Ishida: Kyoto University
R. Peters: Kyoto University
T. Shibauchi: University of Tokyo
A. H. Nevidomskyy: Rice University
L. Qian: Rice University
E. Morosan: Rice University
Y. Matsuda: Kyoto University

Nature Communications, 2022, vol. 13, issue 1, 1-9

Abstract: 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.

Date: 2022
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DOI: 10.1038/s41467-021-27541-9

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