Parallel spin-momentum locking in bulk states of amorphous PtGa

Chiral topological semimetals belong to a new class of topological materials that host new fermionic excitations without analogue in high energy physics. We have recently demonstrated that these new quasiparticles exhibit a new form of isotropic parallel spin-momentum locking and monopoles of orbital-angular momentum (OAM). These remarkable features make them promising candidates for applications in spin-orbitronics, for instance for field-free switching of magnets with perpendicular magnetic anisotropy. One of the open questions is how robust these properties are in the presence of disorder, which inevitably occurs in real devices. It was recently predicted that even in amorphous chiral semimetals, spin- and orbital monopoles could exist as long as a local, short-range chirality is retained. To test this prediction, we propose bulk sensitive (dichroic) soft X-ray spin-ARPES of the prototypical materials candidate PtGa both in the single crystalline and amorphous form.