# Current in nanojunctions : Effects of reservoir coupling

## TL;DR

This paper investigates how the coupling between a quantum system and reservoirs influences electron currents in nanojunctions, revealing non-monotonic behaviors and the roles of eigenstates and coherences.

## Contribution

It provides a detailed analysis of current contributions from eigenstates and coherences, showing their interplay affects net current in quantum dot systems with varying reservoir coupling.

## Key findings

- Current carried by populations is always positive.
- Current carried by coherences becomes negative at large couplings.
- Net current can vanish due to cancellation effects at strong coupling.

## Abstract

We study the effect of system reservoir coupling on currents flowing through quantum junctions. We consider two simple double-quantum dot configurations coupled to two external fermionic reservoirs and study the net current flowing between the two reservoirs. The net current is partitioned into currents carried by the eigenstates of the system and by the coherences between the eigenstates induced due to coupling with the reservoirs. We find that current carried by populations is always positive whereas current carried by coherences are negative for large couplings. This results in a non-monotonic dependence of the net current on the coupling strength. We find that in certain cases, the net current can vanish at large couplings due to cancellation between currents carried by the eigenstates and by the coherences. These results provide new insights into the non-trivial role of system-reservoir couplings on electron transport through quantum dot junctions. In the presence of weak coulomb interactions, net current as a function of system reservoir coupling strength shows similar trends as for the non-interacting case.