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arXiv · 2204.02327

Low-temperature thermal expansion of the topological material candidates $\beta$-PtBi$_2$ and $\beta$-Bi$_2$Pd

V. F. Correa·P. Pedrazzini·D. G. Franco·A. J. Rosa·B. Rubrecht·N. Haberkorn
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Abstract

We report on the low-temperature ($T <$ 120 K) thermal expansion of the bismuth-based topological semimetal $\beta$-PtBi$_2$ and topological superconductor $\beta$-Bi$_2$Pd candidates. The linear thermal-expansion coefficient of tetragonal $\beta$-Bi$_2$Pd shows a pronounced anisotropy between the $a$- and $c$-axis while the volume thermal-expansion coefficient $\alpha_V$($\beta$-Bi$_2$Pd) is considerable larger than $\alpha_V$($\beta$-PtBi$_2$). The coefficient $\alpha_V$($\beta$-PtBi$_2$) nearly matches the experimental specific heat, from which a Debye temperature $\theta_D =$ 199 K is obtained. On the other hand, $\alpha_V$($\beta$-Bi$_2$Pd) reasonably fits the Debye model with $\theta_D =$ 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.

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V. F. Correa, P. Pedrazzini, D. G. Franco, A. J. Rosa, B. Rubrecht, N. Haberkorn. 2022-04-05. Low-temperature thermal expansion of the topological material candidates $\beta$-PtBi$_2$ and $\beta$-Bi$_2$Pd. https://doi.org/10.1016/j.physb.2022.414102

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