Flux-dependent occupations and occupation difference in geometrically symmetric and energy degenerate double-dot Aharonov-Bohm interferometers

TL;DR

This paper investigates how magnetic flux, bias voltage, and gating influence occupation and coherence in a double-dot Aharonov-Bohm interferometer, revealing flux-dependent effects and robustness of coherence even under dephasing.

Contribution

It provides a detailed analysis of flux-dependent occupation and coherence phenomena in a symmetric double-dot interferometer, including effects of dephasing and gating, using analytical and numerical methods.

Findings

Flux controls dot occupation and induces occupation difference.

Coherence persists despite large dephasing, enabling new oscillations.

Gating and magnetic flux offer precise control over quantum dot states.

Abstract

We study the steady-state characteristics and the transient behavior of the nonequilibrium double-dot Aharonov-Bohm interferometer using analytical tools and numerical simulations. Our simple setup includes noninteracting degenerate quantum dots that are coupled to two biased metallic leads at the same strength. A magnetic flux $\Phi$ is piercing the setup perpendicularly. As we tune the degenerate dots energies away from the symmetric point we observe four nontrivial magnetic flux control effects: (i) flux dependency of the dots occupation, (ii) magnetic flux induced occupation difference between the dots, at degeneracy, (iii) the effect of "phase-localization" of the dots coherence holds only at the symmetric point, while in general both real and imaginary parts of the coherence are nonzero, and (iv) coherent evolution survives even when the dephasing strength, introduced into our model using B\"uttiker probe, is large and comparable to the dots energies and the bias voltage. Moreover, not only finite dephasing strength does not destroy the coherence features, it can provide new type of coherent oscillations. These four phenomena take place when the dots energies are gated, to be positioned away from the symmetric point, demonstrating that the combination of bias voltage, magnetic flux and gating field, can provide delicate controllability over the occupation of each of the quantum dots, and their coherence.