Abnormally enhanced Hall Lorenz number in the magnetic Weyl semimetal NdAlSi.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39592608.
- Also identified by DOI 10.1038/s41467-024-54632-0 and PMC identifier 11599383.
- Licence recorded as CC BY-NC-ND.
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Abstract
In Landau's celebrated Fermi liquid theory, electrons in a metal obey the Wiedemann-Franz law at the lowest temperatures. This law states that electron heat and charge transport are linked by a constant L<sub>0</sub>, i.e., the Sommerfeld value of the Lorenz number (L). Such relation can be violated at elevated temperatures where the abundant inelastic scattering leads to a reduction of the Lorenz number (L < L<sub>0</sub>). Here, we report a rare case of remarkably enhanced Lorenz number (L > L<sub>0</sub>) discovered in the magnetic topological semimetal NdAlSi. Measurements of the transverse electrical and thermal transport coefficients reveal that the Hall Lorenz number L<sub>xy</sub> in NdAlSi starts to deviate from the canonical value far above its magnetic ordering temperature. Moreover, L<sub>xy</sub> displays strong nonmonotonic temperature and field dependence, reaching its maximum value close to 2L<sub>0</sub> in an intermediate parameter range. Further analysis excludes charge-neutral excitations as the origin of enhanced L<sub>xy</sub>. Alternatively, we attribute it to the Kondo-type elastic scattering off localized 4f electrons, which creates a peculiar energy distribution of the quasiparticle relaxation time. Our results provide insights into the perplexing transport phenomena caused by the interplay between charge and spin degrees of freedom.