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The origin of the sharpness of the maximum in the phonon thermal conductivity of (Ta1-xNbxSe4)2I at low temperature

Thermal conductivity (K) studies are reported on alloys of the linear-chain compound (TaSe_4)_2I either pure or doped with Nb, in the low-T regime. K(T) varies like T^3 at very low temperatures, in agreement with the boundary scattering regime. At higher T, there is a deviation from T^3, towards T^n with n less than or similar to 2, for doped samples, which can be explained by a scattering process related to impurities. A sharp anomaly appears in the case of pure and doped (1 at% Nb) alloys around 1 and 1.8 K, respectively, which can be related to very unusual phonon properties of these materials and suggests a possible explanation by the Poiseuille effect.

thermal conductivtiy ; scattering processes ; (TaSe4)2I

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