Evaluating the Wiedemann-Franz Law in Compressively Strained HgTe Weyl Semimetal

Dirac and Weyl semimetals have captured widespread attention due to their unique linear band crossings in three dimensions, allowing the exploration of Weyl and Dirac quasiparticles and related quantum anomalies. In this study, we probe the thermal conductance of a Weyl semimetal based on a compressively strained HgTe film and its correlation to the anticipated gravitational anomaly. The Weyl regime is precisely accessed by Fermi level tuning and the thermal conductance is accurately determined by measuring the electron temperature using Johnson noise thermometry at liquid helium temperature. We observe a positive magneto-thermal conductance that is consistent with the predictions related to gravitational anomaly. However, it perfectly aligns with the electrical conductance predicted by the Wiedemann-Franz law. This suggests that mechanisms driving both the heat and the electrical transport are the same with no involvement of any anomalous mechanisms of heat transport. Additionally, thermopower measurements from the same device align with Mott's relation, further substantiating these conclusions.