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arXiv · 2209.10844

Enhancement of charge-neutral fermionic excitation near spin-flop transition\\ in magnetic Kondo material YbIr$_3$Si$_7$

Shunsaku Kitagawa·Takumi Kobayashi·Fumiya Hori·Kenji Ishida·Andriy H. Nevidomskyy·Long Qian·Emilia Morosan
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Abstract

The new Kondo material YbIr$_3$Si$_7$, similar to other Kondo insulators, has been reported to exhibit charge-neutral fermionic excitations through measurements of specific heat and thermal conductivity at low temperatures. We performed $^{29}$Si-NMR on YbIr$_3$Si$_7$ to investigate the magnetic response of charge-neutral fermions from a microscopic perspective. In low magnetic fields parallel to the $c$ axis, a single NMR peak in the paramagnetic state splits into three peaks below $T_{\rm N}$. In contrast, only a slight shift of the single NMR peak was observed in high magnetic fields. This spectral change as a function of the $c$-axis magnetic field is interpreted as spin-flop transition, at which the magnetic moments oriented along the $c$ axis (AF-I phase) are rotated to the $ab$ plane with ferromagnetic component along the $c$-axis (AF-II phase). In the vicinity of the spin-flop magnetic field $H_{\rm M}$, nuclear spin-lattice relaxation rate $1/T_1$ was found to be proportional to temperature at low temperatures, indicating the existence of charge-neutral fermions. Furthermore, a peak of $1/T_1$ vs. the $c$-axis magnetic field suggests that the charge-neutral fermions in YbIr$_3$Si$_7$ are closely related to its magnetic properties. Our findings shed light on the origin of charge-neutral fermions in insulators.

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Shunsaku Kitagawa, Takumi Kobayashi, Fumiya Hori, Kenji Ishida, Andriy H. Nevidomskyy, Long Qian, Emilia Morosan. 2022-09-22. Enhancement of charge-neutral fermionic excitation near spin-flop transition\\ in magnetic Kondo material YbIr$_3$Si$_7$. https://doi.org/10.1103/physrevb.106.l100405

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