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arXiv · 2102.08615

Field-induced valence fluctuation in YbB$_{12}$

R. Kurihara·A. Miyake·M. Tokunaga·A. Ikeda·Y. H. Matsuda·A. Miyata·D. I. Gorbunov·T. Nomura·S. Zherlitsyn·J. Wosnitza·F. Iga
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Abstract

We performed high-magnetic-field ultrasonic experiments on YbB$_{12}$ up to 59 T to investigate the valence fluctuations in Yb ions. In zero field, the longitudinal elastic constant $C_{11}$, the transverse elastic constants $C_{44}$ and $\left( C_{11} - C_{12} \right)/2$, and the bulk modulus $C_\mathrm{B}$ show a hardening with a change of curvature at around 35 K indicating a small contribution of valence fluctuations to the elastic constants. When high magnetic fields are applied at low temperatures, $C_\mathrm{B}$ exhibits a softening above a field-induced insulator-metal transition signaling field-induced valence fluctuations. Furthermore, at elevated temperatures, the field-induced softening of $C_\mathrm{B}$ takes place at even lower fields and $C_\mathrm{B}$ decreases continuously with field. Our analysis using the multipole susceptibility based on a two-band model reveals that the softening of $C_\mathrm{B}$ originates from the enhancement of multipole-strain interaction in addition to the decrease of the insulator energy gap. This analysis indicates that field-induced valence fluctuations of Yb cause the instability of the bulk modulus $C_\mathrm{B}$.

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R. Kurihara, A. Miyake, M. Tokunaga, A. Ikeda, Y. H. Matsuda, A. Miyata, D. I. Gorbunov, T. Nomura, S. Zherlitsyn, J. Wosnitza, F. Iga. 2021-02-17. Field-induced valence fluctuation in YbB$_{12}$. https://doi.org/10.1103/physrevb.103.115103

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