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Correa, V. F., P. Pedrazzini, D. G. Franco, A. J. Rosa, B. Rubrecht, N. Haberkorn. "Low-temperature thermal expansion of the topological material candidates β-PtBi2 and β-PdBi2." Physica B – Condensed Matter 641 (2022): 414102.
Abstract: We report on the low-temperature ($T <$ 120 K) thermal expansion of the bismuth-based topological semimetal $\beta$-PtBi$2$ and topological superconductor $\beta$-PdBi$2$ candidates.
The linear thermal-expansion coefficient of tetragonal $\beta$-PdBi$2$ shows a pronounced anisotropy between the $a$- and $c$-axis while the volume thermal-expansion coefficient $\alphaV$($\beta$-PdBi$2$) is considerable larger than $\alphaV$($\beta$-PtBi$_2$).
The coefficient $\alphaV$($\beta$-PtBi$2$) nearly matches the experimental specific heat, from which a Debye temperature $\thetaD =$ 199 K is obtained. On the other hand, $\alphaV$($\beta$-PdBi$2$) reasonably fits the Debye model with $\thetaD =$ 138 K, extracted from the low-temperature specific heat.
An almost constant Gr\"uneisen parameter $\Gamma \approx$ 2 is obtained for both compounds.
No magnetostriction is observed in any of both compounds up to $\mu_0 H =$ 16 T.
We compare our results with other Bi-based topological materials.