Tuning the Weyl semimetal CeAlSi by external pressure

The search for materials hosting non-trivial topological phases receives a lot of effort of the condensed matter physics community due to its unusual transport properties, such as ultrahigh mobility, anomalous Hall effect and extremely large magnetoresistance, which may enable the development of future technology applications, such as spintronic and new memory recording devices. Moreover, the presence of Ce ions is expected to induce other complex properties in the materials, such as magnetism, Kondo effect and crystalline electrical field effects, which interplay and relation to topological phases are rather unexplored. For instance, the Kondo effect may favor non-trivial topological properties by pinning band crossings near the Fermi energy [1].
Here we focus on the Weyl semimetal CeAlSi, which crystallizes in the noncentrosymmetric structure ($I4_{1}md$) and presents a noncollinear ferromagnetic order below 8.2 K showing an anisotropic anomalous Hall effect [2]. Moreover, chiral domain walls were recently observed in this material [3,4]. By combining electrical resistivity, Hall effect, and magnetization measurements with pressure tuning and DFT calculations, we were able to fully investigate the non-trivial topological properties of CeAlSi. Our results confirm the anisotropic anomalous Hall effect and revealed an unexpected temperature response of the quantum oscillations amplitude. The application of external pressure suppresses both behaviors; however, it favors the ferromagnetism, enhancing $T_{C}$ to 9.4 K at 2.7 GPa. No evidence of changes in the magnetic structure was observed. Finally, DFT calculations show negligible changes in the position of the Weyl nodes as a function of pressure. We may therefore speculate that the suppression of the anomalous responses of the Hall effect and the quantum oscillations amplitude might be related to the non-trivial topology domain walls present in this system.