Glass-like thermal conductivity and narrow insulating gap of EuTiO$_3$

Alexandre Jaoui; Shan Jiang; Xiaokang Li; Yasuhide Tomioka; Isao H. Inoue; Johannes Engelmayer; Rohit Sharma; Lara Pätzold; Thomas Lorenz; Benoît Fauqué; Kamran Behnia

arXiv · 2307.02058

Glass-like thermal conductivity and narrow insulating gap of EuTiO$_3$

Alexandre Jaoui·Shan Jiang·Xiaokang Li·Yasuhide Tomioka·Isao H. Inoue·Johannes Engelmayer·Rohit Sharma·Lara Pätzold·Thomas Lorenz·Benoît Fauqué·Kamran Behnia

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Abstract

Crystals and glasses differ by the amplitude and the temperature dependence of their thermal conductivity. However, there are crystals known to display glass-like thermal conductivity. Here, we show that EuTiO$_3$, a quantum paraelectric known to order antiferromagnetically at 5.5 K, is one such system. The temperature dependence of resistivity and Seebeck coefficient yield an insulating band gap of $\sim 0.22$ eV. Thermal conductivity is drastically reduced. Its amplitude and temperature dependence are akin to what is seen in amorphous silica. Comparison with non-magnetic perovskite solids, SrTiO$_3$, KTaO$_3$, and EuCoO$_3$, shows that what impedes heat transport are $4f$ spins at Eu$^{2+}$ sites, which couple to phonons well above the ordering temperature. Thus, in this case, superexchange and valence fluctuations, not magnetic frustration, are the drivers of the glass-like thermal conductivity.

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Alexandre Jaoui, Shan Jiang, Xiaokang Li, Yasuhide Tomioka, Isao H. Inoue, Johannes Engelmayer, Rohit Sharma, Lara Pätzold, Thomas Lorenz, Benoît Fauqué, Kamran Behnia. 2023-07-05. Glass-like thermal conductivity and narrow insulating gap of EuTiO$_3$. https://arxiv.org/abs/2307.02058

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