G. C. Strinati

Application of the Green’s functions method to the study of the optical properties of semiconductors

75 APPENDIX E. 77 APPENDIX F. 79 APPENDIX G. 82 APPENDIX H. Introduction. Generalized Greens functions. Equations of motion for the generalized single-particle Greens function. Bethe-Salpeter equation for the two-particle Greens function. Connection with linear-response theory. Conserving approximations. Gauge invariance, current conservation, and the Ward identities. Optical properties of semiconductors. Single-particle energy levels. Screening of static impurities. Excitonic states. A functional derivative identity. Dysons equation. Reducible vs. irreducible parts of the correlation functions. Elimination of the spin variables and transformation to the energy-momentum representation. The Thomas-Reiche-Kuhn sum rule. The Clausius-Mossotti relation. The particle-hole Greens function. The Haken potential.

Observation of pseudogap behaviour in a strongly interacting Fermi gas

An ultracold gas of strongly interacting fermions exhibits a pseudogap phase in which pairs of fermions exist above the superfluid transition, but lack the phase coherence of a superfluid.

BCS-BEC Crossover at Finite Temperature for Superfluid Trapped Fermi Atoms

We consider the BCS-BEC (Bose-Einstein-condensate) crossover for a system of trapped Fermi atoms at finite temperature, both below and above the superfluid critical temperature, by including fluctuations beyond mean field. We determine the superfluid critical temperature and the pair-breaking temperature as functions of the attractive interaction between Fermi atoms, from the weak- to the strong-coupling limit (where bosonic molecules form as bound-fermion pairs). Density profiles in the trap are also obtained for all temperatures and couplings.

Pseudogap and spectral function from superconducting fluctuations to the bosonic limit

The crossover from weak to strong coupling for a three-dimensional continuum model of fermions interacting via an attractive contact potential is studied above the superconducting critical temperature

Quantitative comparison between theoretical predictions and experimental results for the BCS-BEC crossover

{T}_{c}.

Evolution from BCS superconductivity to Bose condensation: analytic results for the crossover in three dimensions

The pair-fluctuation propagator, the one-loop self-energy, and the spectral function are investigated in a systematic way from the superconducting fluctuation regime (weak coupling) to the bosonic regime (strong coupling). Analytic and numerical results are reported. In the strong-coupling regime, where the pair fluctuation propagator has bosonic character, two quite different peaks appear in the spectral function at a given wave vector, a broad one at negative frequencies and a narrow one at positive frequencies. The broad peak is asymmetric about its maximum, with its spectral weight decreasing by increasing coupling and temperature. In this regime, two crossover temperatures

Derivation of the Gross-Pitaevskii equation for condensed bosons from the Bogoliubov-de Gennes equations for superfluid fermions

{T}_{1}^{*}

Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas

(at which the two peaks in the spectral function merge in one peak) and

Trapped Fermions with Density Imbalance in the Bose-Einstein Condensate Limit

{T}_{0}^{*}

Density-induced BCS to Bose-Einstein crossover

(at which the maximum of the lower peak crosses zero frequency) can be identified, with