Nonreciprocal ballistic transport in multilayer Weyl semimetal films with surface engineering

Weyl semimetal (WSM) thin films exhibit distinct electronic properties compared to their bulk counterparts. In this study, we theoretically investigate the nonreciprocal ballistic transport phenomena arising in WSM thin films due to surface modifications. Our analysis demonstrates that the nonreciprocity is sub-band resolved, where the surface states provide the dominant contribution to the nonreciprocity, whereas the bulk states introduce a negative correction. The striking contrast of the second-order conductance signal may serve as evidence for the existence of surface states. Our calculations further reveal a quantum size effect: overall, the nonreciprocal signal decreases with increasing film thickness, but it undergoes discontinuities as the Fermi energy approaches the bottom of a sub-band. Moreover, we observe a special sub-band-resolved pattern of density of states (DOS), which is common in multilayer systems.