Geometry-Enforced Topological Chiral Fermions in Amorphous Chiral Metals

The recent recognition of a link between topological and structural chirality precipitated the experimental discovery of large families of ideal topological chiral (e.g. Weyl) semimetals, such as B-20 RhSi, with dramatic long topological surface Fermi arcs and tunable chirality-dependent spin, orbital, and response properties.

However outside of the limit of perfect translation symmetry, especially among the numerous experimentally accessible amorphous materials in nature, it remains an open question whether there similarly exist mechanisms for generating and identifying topologically chiral nodal degeneracies.

We present extensive analytic and numerical calculations demonstrating the existence of multitudinous chiral fermions in amorphous metals, whose degeneracy and chiral charges are tunable via the interplay of average symmetry and geometry.

We introduce an amorphous Wilson-loop numerical method to, for the first time, characterize chiral fermions with quantized Berry curvature fluxes in fully disordered 3D metals.

We further analyze the role of disorder on the bulk-boundary correspondence and response.

Our findings indicate a clear route towards engineering geometry-enforced topology in non-crystalline materials and metamaterials.