Coherent quantum transport in the presence of a finite-range transversely polarized time-dependent field

This work investigates the quantum transport in a narrow constriction acted upon by a finite-range transversely polarized time-dependent field. A gene ralized scattering-matrix method is developed that has incorporated a time- dependent mode-matching scheme. The transverse field induces coherent inela stic scatterings that include both intersubband and intersideband transitio ns. These scatterings give rise to the DC conductance G a general suppresse d feature that escalates with the chemical potential. In addition, particul ar suppressed features - the dip structures - are found in G. These feature s are recognized as the quasibound state (QBS) features that arise from ele ctrons making intersubband transitions to the vicinity of a subband bottom. For the case of larger held intensities, the QBS features that involve mor e photons are more evident. These QBS features are closely associated with the singular density of states at the subband threshold. An experimental se tup is proposed for the observation of these features. (C) 2000 Elsevier Sc ience B.V. All rights reserved.