Weyl fermion-based spin current generation (WeylSPIN)

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Owing to their topologically protected, helical spin texture, Weyl semimetals are promising as electrically driven spin generators. The present project aims at gaining a fundamental understanding of the spin currents and spin dynamics in multi- and monolayers of the two type-II Weyl semimetals WTe2 and MoTe2. To reach this task, we plan to combine magnetic transport spectroscopy experiments, which can yield the spin polarisation, with time- and spatially-resolved helical photocurrent and -conductance measurements, which can provide the spin relaxation times. By gaining access to both, spin polarisation and relaxation times for one-and-the-same samples studied in the two groups, we envision determining the relevant “optoelectronic” times and underlying scattering mechanisms for the crystallographic direction-dependent spin and charge transport processes in the ultrathin sheets. Further objectives are to identify the individual contributions of the bulk and surface states to the spin current generation, as well as to clarify in detail the influence of the two possible crystal phases and the number of monolayers. For the later project stage, we intend demonstrating a Berry curvature-based switching of the spin current generation by an electrostatic gate field, along with evaluating the corresponding transport time scales and signatures.