We predict a new surface polariton mode in semiconductors with split exciton bands with linear in the wave vector. It is the only surface polariton whose existence is a result of spatial dispersion (nonlocal effects). Calculated attenuated-total-reflection spectra for the B(n=1) exciton of CdS exhibit a well-defined minimum corresponding to this mode, in addition to the usual minimum (which persists even in the local limit).

• Received 17 June 1985

DOI:https://doi.org/10.1103/PhysRevB.32.6986