Excitons dressed by a sea of excitons

Abstract

We here consider an exciton $i$ embedded in a sea of $N$ identical excitons 0. If the excitons are bosonized, a bosonic enhancement factor, proportional to $N$, is found for $i=0$. If the exciton composite nature is kept, this enhancement not only exists for $i=0$, but also for any exciton having a center of mass momentum equal to the sea exciton momentum. This physically comes from the fact that an exciton with such a momentum can be transformed into a sea exciton by ``Pauli scattering'', \emph{i}. \emph{e}., carrier exchange with the sea, making this $i$ exciton not so much different from a 0 exciton. This possible scattering, directly linked to the composite nature of the excitons, is irretrievably lost when the excitons are bosonized. This work in fact deals with the quite tricky scalar products of $N$-exciton states. It actually constitutes a crucial piece of our new many-body theory for interacting composite bosons, because all physical effects involving these composite bosons ultimately end by calculating such scalar products. The ``Pauli diagrams'' we here introduce to represent them, allow to visualize many-body effects linked to carrier exchange in an easy way. They are conceptually different from Feynman diagrams, because of the special feature of the ``Pauli scatterings'': These scatterings, which originate from the departure from boson statistics, do not have their equivalent in Feynman diagrams, the commutation rules for exact bosons (or fermions) being included in the first line of the usual many-body theories.

References in corpus (6)

• On the correct strong-coupling limit in the evolution from BCS superconductivity to Bose-Einstein condensation
• The Effective Bosonic Hamiltonian for Excitons Reconsidered
• New criteria for bosonic behavior of excitons
• Commutation technique for interacting close-to-boson excitons
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Cited by in corpus (3)

• Faraday rotation in photoexcited semiconductors: an excitonic many-body effect
• Biexciton oscillator strength
• How composite bosons really interact