Transport characteristics of bulk and edge states in an off-diagonal Aubry-André-Harper chain.

We investigate quantum transport in an off-diagonal Aubry--Andr'{e}--Harper chain. For a commensurate hopping modulation, the periodic hopping pattern can generate internal boundaries that strongly influence the transmission characteristics. We show that edge, in-band bulk, and band-edge bulk states can be distinguished through their distinct transport signatures. In particular, bulk states near the band edges exhibit transport characteristics similar to those of edge states, with weak dependence on system size, whereas in-band bulk states display pronounced size-dependent oscillations. We further demonstrate that the chain--electrode coupling strength controls the broadening of transmission resonances and drives a crossover from tunneling-dominated to nearly ballistic transport. In addition, dephasing produces distinct responses among the different state classes, reflecting their different spatial structures and dependence on phase coherence. These results highlight the roles of commensurate hopping modulation, electrode geometry, and quantum coherence in controlling transport in modulated one-dimensional systems.