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Accueil du site > Équipes scientifiques > Dynamiques et Interactions : Rayonnement, Atomes, Molécules (DIRAM) > Cohérence et contrôle de la dynamique quantique > Fano goes Nano

Fano goes Nano

par Keller Arne - 3 septembre 2015

Fano Interferences occur when a quantum system can follow two pathways to its fragmentation. In an article to appear in Physical Review Letters Daniel Finkelstein-Shapiro has revisited this fundamental phenomenon in the framework of an international collaboration bringing together researchers from Laboratoire de Chimie Théorique of the Université Pierre et Marie Curie, from the Department of Chemistry and Biochemistry Chemistry Département of the Arizona State University and from ISMO.

One of the clear-cut signatures of a quantum process is that of interference, where for example a particle which can follow two pathways to reach a final state cannot reach its destination even if both pathways are open because of a destructive interference. The peculiarity of Fano interference phenomenon is that the final destination involves an infinite continuum set of available states. Fano interferences have first been observed in photoionization experiments with atoms in 1935 and explained by Ugo Fano in a famous paper in 1961. Recently, with the advent of nanotechnology, researchers have observed similar quantum signatures but the original theory is now outdated. In this Letter, we have revisited this important theory and reformulated it such that it is suitable for nanotechnology in order to accurately describe and inspire new devices.

Profils de Fano

Fano-Liouville Spectral Signatures in Open Quantum Systems

Fano Interferences occur when a quantum system can follow two pathways to dissociation or fragmentation : a direct pathway and an indirect one through a metastable state with a finite lifetime. This phenomenon was first observed in 1935 by H. Beutler for the photo-ionization of Helium atom. These quantum interferences induce a characteristic asymmetric shape of the atomic absorption spectrum. The same year, a first theoretical interpretation was given by Fano, who generalized his results later in 1961, in a paper, which is still celebrated, as one of the few articles ever published by Physical Review that have been cited more than 1000 times.

Since then, Fano interferences have been described in several atomic and molecular systems. Recently, same type of processes have been observed in several nanostructured systems, like plasmonic systems, quantum dots semiconductor devices or in molecules adsorbed on metallic surfaces, to name a few.

Daniel Finkelstein-Shapiro has revisited this fundamental phenomenon in the framework of an international collaboration bringing together researchers from Laboratoire de Chimie Théorique of the Université Pierre et Marie Curie, from the Department of Chemistry and Biochemistry Chemistry Département of the Arizona State University and from ISMO.

The work consist in a generalizing the Fano model in two directions : a complete description of the light emission by the quantum system, and taking into account the dissipation and relaxation processes. In that way, Rayleigh, Raman and fluorescence spectra are calculated and explicit expression are obtained.

These theoretical results will allow a more detailed interpretation of many spectroscopy experiments in which Fano interferences are nowadays observed, and permit to infer relaxation rate constants of the quantum system under study. They also pave the way to suggest new experiments for the design of nano-optical devices that can make use of this fascinating effect.

arXiv : http://arxiv.org/abs/1503.03051 Fano-Liouville spectral signatures in open quantum systems Daniel Finkelstein-Shapiro, Ines Urdaneta, Monica Calatayud, Osman Atabek, Vladimiro Mujica, and Arne Keller