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arXiv · 1508.06481

Low-temperature thermal conductivity of Dy_2Ti_2O_7 and Yb_2Ti_2O_7 single crystals

S. J. Li·Z. Y. Zhao·C. Fan·B. Tong·F. B. Zhang·J. Shi·J. C. Wu·X. G. Li·H. D. Zhou·X. Zhao·X. F. Sun
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Abstract

We study the low-temperature thermal conductivity (κ) of Dy_2Ti_2O_7 and Yb_2Ti_2O_7 single crystals in magnetic fields up to 14 T along the [111], [100] and [110] directions. The main experimental findings for Dy_2Ti_2O_7 are: (i) the low-T κ(H) isotherms exhibit not only the step-like decreases at the low-field (< 2 T) magnetic transitions but also obvious field dependencies in high fields (> 7 T); (ii) at T \le 0.5 K, the κ(H) curves show anisotropic irreversibility in low fields, that is, the κ(H) hysteresis locates at the first-order transition with H \parallel [100] and [110], while it locates between two successive transitions with H \parallel [111]; (iii) the κin the hysteresis loops for H \parallel [100] and [110] show an extremely slow relaxation with the time constant of \sim 1000 min. The main experimental findings for Yb_2Ti_2O_7 are: (i) the zero-field κ(T) show a kink-like decrease at the first-order transition (\sim 200 mK) with decreasing temperature; (ii) the low-T κ(H) isotherms show a decrease in low field and a large enhancement in high fields; (iii) the low-T κ(H) curves show a sharp minimum at 0.5 T for H \parallel [110] and [111]. The roles of monopole excitations, field-induced transitions, spin fluctuations and magnetoelastic coupling are discussed.

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S. J. Li, Z. Y. Zhao, C. Fan, B. Tong, F. B. Zhang, J. Shi, J. C. Wu, X. G. Li, H. D. Zhou, X. Zhao, X. F. Sun. 2015-08-26. Low-temperature thermal conductivity of Dy_2Ti_2O_7 and Yb_2Ti_2O_7 single crystals. https://doi.org/10.1103/physrevb.92.094408

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