Transmission, S-matrix, and partial densities of states for ac transport through a resonant cavity with multileads

We investigate the principal properties of ac transport through a resonant cavity with multileads. In terms of Green’s function and the coupling strengths of the system, a set of general expressions for the partial densities of states ~PDOS! can be derived in an unambiguous way. In particular we derive the PDOS with a reflection property. All the PDOS’s are in an explicit and compact form. Based upon these PDOS’s, the ac conductance can be calculated to a first-order frequency-dependent term. As an extension, we introduce the second-order nonlinear PDOS; then the ac conductance can be generalized to include the second-order contribution. As an example, we apply these formulas to evaluate the linear emittance and the second-order nonlinear emittance in a simplified structure. Some interesting results are obtained.