Charge to spin conversion in the Weyl semimetal NbAs

The search for novel topological quantum materials where spin can be controlled electrically is a fundamental scientific aim that might impact the development of low power spin-orbit torque memory devices. In this context, we study charge to spin conversion in thin films of the Weyl semimetal NbAs. We use molecular beam epitaxy to grow it on different III-V semiconductor substrates and perform careful x-ray diffraction and transmission electron microscopy characterization. We show that our films are textured with a defined crystalline orientation that depends on the substrate orientation. We combine them with the metallic ferromagnet permalloy and use spin torque ferromagnetic resonance to show charge to spin conversion at room temperature in the heterostructure. Finally, we combine this measurements with electrical transport characterization, compute the efficiency of the conversion and determine the spin Hall conductivity of NbAs