Synthesis of a thin film Weyl ferromagnet

High-quality, tunable materials drive quantum physics. In the case of Weyl materials, many of the key breakthroughs have been made using single crystals [1-4]. Thin film Weyl semimetals offer the promise of exceptional tunability, design of novel hetero-interfaces, and the development of new electronic and optical components. Although several Weyl materials have been synthesized in thin film form, these are typically polycrystalline, have low mobility, or are difficult to electronically engineer. I will report on our development of a novel high-mobility, crystalline, thin film Weyl ferromagnet. Through measurements of the anomalous Hall effect and chiral anomaly, we provide evidence for Weyl fermions in the bulk of our film. Leveraging the unique strengths of state-of-the-art molecular beam epitaxy (MBE), we are further able to exceed the bulk dopant solubility limit and widely tune the electronic structure, demonstrating the creation and annihilation of Weyl fermions. Our thin films provide a unique platform for Weyl superconductors, Weyl thermoelectrics and neuromorphic computing [4,5].

[1] Tokura, Yasuda and Tsukazaki, Nat. Rev. Phys. 1, 126 (2019).

[2] Hasan, Chang, Belopolski et al., Nat. Rev. Mat. 6, 784 (2021).

[3] Belopolski et al., Nature 604, 647 (2022).

[4] Zhang et al., PNAS 118 (44), e2111855118 (2021).

[5] Masuko et al., npj Quant. Mat. 7, 104 (2022).