Coulomb interaction and transient charging of excited states in open nanosystems

Abstract

We obtain and analyze the effect of electron-electron Coulomb interaction on the time-dependent current flowing through a mesoscopic system connected to biased semi-infinite leads. We assume the contact is gradually switched on in time and we calculate the time-dependent reduced density operator of the sample using the generalized master equation. The many-electron states ͑MES͒ of the isolated sample are derived with the exact-diagonalization method. The chemical potentials of the two leads create a bias window which determines which MES are relevant to the charging and discharging of the sample and to the currents, during the transient or steady states. We discuss the contribution of the MES with fixed number of electrons N and we find that in the transient regime there are excited states more active than the ground state even for N = 1. This is a dynamical signature of the Coulomb-blockade phenomenon. We discuss numerical results for three sample models: short one-dimensional chain, two-dimensional ͑2D͒ lattice, and 2D parabolic quantum wire.

Spin-dependent heat and thermoelectric currents in a Rashba ring coupled to a photon cavity

“…The GME is derived according to a Nakajima-Zwanzig projection approach with the coupling Hamiltonian entering the dissipation kernel of the integro-differential equation up to second order. The coupling of the central system and the leads is expressed by a many-body coupling tensor derived from the geometry of the single-electrons states in the contact area of the leads and system [27,28].…”

“…where the charge operator isQ = e d 2 rΨ † (r)Ψ(r) [27,28]. In the next section, we present our main results of the thermal transport of a quantum ring coupled to a photon field.…”

Time-dependent bond-current functional theory for lattice Hamiltonians: Fundamental theorem and application to electron transport

“…Although most of these studies are restricted to the steady-state regime, more recently there has been increasing activity to describe the time evolution towards the steady state as the system is driven out of equilibrium by applying a bias in the leads. These studies use a range of methods such as, e.g., TDDFT [2,[17][18][19][20], generalized master equations [21], many-body perturbation theory [22][23][24], the timedependent density-matrix renormalization group [25][26][27], a quantum trajectory approach [28], or real-time path integral [29] and Monte Carlo approaches [30].…”

Optical switching of electron transport in a waveguide-QED system

“…Our approach here is to use a singlephoton mode to manipulate the electron motion between the two waveguides in two regimes, for off-and resonant photon field. The transient electron transport in the waveguide system is described using a generalized master equation [13,14]. The switching processes implement the quantum logic gate actions in the double waveguide system representing the quantum bit.…”