A quantum many-body density matrix model for sub-femtosecond transport in mesoscopic structures

Transient regime relaxation in nanostructures is governed by the two-way information exchange between the active region and the contacts. In this paper, we introduce a second order quantum master equation for the active region's many-body reduced density matrix, which includes the information exchange between the active region and the contacts, while eliminating the contacts explicitly from the simulation. For the case of a resonant-tunneling diode, the master equation is solved numerically. Proper injection from/into the contacts is obtained, and natural oscillations of the current and the number of particles in the well are observed, with a frequency in the mid-terahertz regime.