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The flow equation approach to the pairing instability problem

T. Domanski·A. Donabidowicz
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Abstract

By means of the continuous unitary transformation similar to a general scheme of the Renormalization Group (RG) procedure we study the issue of symmetry breaking and pairing instability in the system of interacting fermions. Constructing a generalized version of the Bogoliubov transformation we show that formation of the fermion pairs and their superconductivity/superfluidity can appear at different temperatures. It is shown that strong quantum fluctuations can destroy the long-range order without breaking the fermion pairs which may still exist as incoherent and/or damped entities. Such unusual phase is characterized by a partial suppression of the density of states near the Fermi energy and by residual collective features like the sound-wave mode in the fermion pair spectrum.

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T. Domanski, A. Donabidowicz. 2006-10-17. The flow equation approach to the pairing instability problem. https://doi.org/10.1142/s0218301307005703

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