Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

Weyl semimetals are characterized by the presence of massless band dispersion in momentum space. When a Weyl semimetal meets magnetism, large anomalous transport properties emerge as a consequence of its topological nature. Here, using in−situ spin- and angle-resolved photoelectron spectroscopy combined with ab initio calculations, we visualize the spin-polarized Weyl cone and flat-band surface states of ferromagnetic Co 2 MnGa films with full remanent magnetization. We demonstrate that the anomalous Hall and Nernst conductivities systematically grow when the magnetization-induced massive Weyl cone at a Lifshitz quantum critical point approaches the Fermi energy, until a high anomalous Nernst thermopower of ~6.2 μVK −1 is realized at room temperature. Given this topological quantum state and full remanent magnetization, Co 2 MnGa films are promising for realizing high efficiency heat flux and magnetic field sensing devices operable at room temperature and zero-field. Topological Weyl semimetals are promising materials for achieving large anomalous Hall and Nernst effects needed in magnetic and heat flux sensors. Here, the authors visualize the spin-polarized Weyl cone and surface states of ferromagnetic Co 2 MnGa films, finding a high Nernst thermopower of 6.2 μ VK −1 .