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Abstract
We study the quantum interference (QI) effects in three-terminal Andreev interferometers based on polyaromatic hydrocarbons (PAHs) under non-equilibrium conditions. The Andreev interferometer consists of a PAH coupled to two superconducting and one normal conducting terminals. We calculate the current measured in the normal lead as well as the current between the superconducting terminals under non-equilibrium conditions. We show that both the QI arising in the PAH cores and the bias voltage applied to a normal contact have a fundamental effect on the charge distribution associated with the Andreev Bound States (ABSs). QI can lead to a peculiar dependence of the normal current on the superconducting phase difference that was not observed in earlier studies of mesoscopic Andreev interferometers. We explain our results by an induced asymmetry in the spatial distribution of the electron- and hole-like quasiparticles. The non-equilibrium charge occupation induced in the central PAH core can result in a transition in the current-phase relation of the supercurrent for large enough applied bias voltage on the normal lead. The asymmetry in the spatial distribution of the electron- and hole-like quasiparticles might be used to split Cooper pairs and hence to produce entangled electrons in four terminal setups.
Highlights
Quantum interference (QI) is ubiquitous in nature
We only mention that the term “weak coupling” means that the central aromatic molecule is weakly coupled to the contacts resulting in a small level broadening and self energy correction to the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels compared to the HOMO-LUMO gap
In the simplest theoretical description an integer valued connectivity matrix Hmol captures the complexity of the inner Constructive quantum interference (CQI) and destructive quantum interference (DQI) effects within the core of the molecule and when EF coincides with the middle of the HOMO-LUMO gap, the resulting magic number matrix Mkl is a table of integers
Summary
Quantum interference (QI) is ubiquitous in nature. Constructive quantum interference (CQI) leads to the formation of energy levels in atoms or molecules and energy bands in crystals, whereas destructive quantum interference (DQI) leads to energy gaps in molecules and band gaps in solids. At lower temperatures, quantum engineers strive to utilise QI in superconducting structures such as superconductor quantum interference devices (SQUIDs) and Andreev interferometers, which rely on controlling the interplay between a superconducting condensate and charge-carrying quasi-particles [14,15,16,17,18,19,20,21,22]. In such devices, QI is controlled by the phase of the superconducting order parameter, which describes a macroscopic collective degree of freedom, which has no counterpart at room temperature
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