# Open system approach to non-equilibrium dynamical theory of quantum dot systems

## TL;DR

This paper develops a non-equilibrium dynamical theory for quantum dot systems using stochastic fermionic quantum state diffusion, revealing complex Coulomb blockade phenomena and non-Markovian effects in electron transport.

## Contribution

It introduces a novel non-equilibrium quantum dynamical framework for quantum dots coupled to reservoirs, capturing transient and steady-state behaviors beyond traditional methods.

## Key findings

- Coulomb blockade observed in spin-degenerate and non-degenerate quantum dots.
- Non-monotonic current behavior with Coulomb energy in spin-degenerate case.
- Significant non-Markovian effects influencing steady-state currents.

## Abstract

We theoretically investigate the non-equilibrium quantum dynamical theory of a quantum dot system coupled to fermionic reservoirs using the recently developed stochastic fermionic quantum state diffusion (FQSD) equation. The exact or approximate dynamical equations associated with the FQSD equation can describe the non-equilibrium quantum transport processes beyond the long-time limit leading to a steady state. We study in details the electron transport of a quantum-dot system coupled to two fermionic environments with different chemical potentials. We report the onset of Coulomb blockade in quantum dots in two distinctive cases: one involving a spin degeneracy one-quantum dot model, and the other a specific spin non-degeneracy two-quantum dot model. While the spin degeneracy case shows that the current in the quantum dot may be blockaded non-monotonically with respect to Coulomb energy, the non-degeneracy case exhibits significant non-Markovian effects, and it enables us to study the relations between initial conditions of the dots and the steady state currents.