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YbB₁₂ is a topological Kondo insulator candidate with recent reports of charge-neutral excitations and quantum oscillations at the lowest temperatures [1-3]. These reports of Fermi-like behavior are unconventional in this bulk insulator, motivating further study of such exotic bulk insulating phenomena. In particular, the experimental study of charge-neutral excitations in YbB₁₂ assists in characterizing these itinerant excitations in order to reliably realize them in real materials. Thermal conductivity is a useful tool for measuring the mobility of such excitations in an insulating bulk.

 

We report thermal conductivity measurements of two YbB₁₂ single crystals at temperatures from 0.1 K to 50 K and fields up to 12 T. A comparison of thermal conductivity measurements suggests that novel excitations may be obscured by phonon scattering of a non-magnetic origin. Therefore, a careful analysis of phonon scattering sources is required to accurately identify these charge-neutral excitations in thermal transport measurements.

 

[1] H. Liu et al., J. Phys: Condens. Matter 30, 16LT01 (2018).

[2] Y. Sato et al., Nat. Phys. 15, 954-959 (2019).

[3] Xiang et al., Science 362, 65–69 (2018).