11 research outputs found
Spin Transport in Cold Fermi gases: A Pseudogap Interpretation of Spin Diffusion Experiments at Unitarity
We address recent spin transport experiments in ultracold unitary Fermi
gases. We provide a theoretical understanding for how the measured temperature
dependence of the spin diffusivity at low can disagree with the expected
behavior of a Fermi liquid (FL) while the spin susceptiblity(following the
experimental protocols) is consistent with a Fermi liquid picture. We show that
the experimental protocols for extracting are based on a FL
presumption; relaxing this leads to consistency within (but not proof of) a
pseudogap-based approach. Our tranport calculations yield insight into the
measured strong suppression of the spin diffusion constant at lower .Comment: 4 pages, 2 figure
Unconventional particle-hole mixing in the systems with strong superconducting fluctuations
Development of the STM and ARPES spectroscopies enabled to reach the
resolution level sufficient for detecting the particle-hole entanglement in
superconducting materials. On a quantitative level one can characterize such
entanglement in terms of the, so called, Bogoliubov angle which determines to
what extent the particles and holes constitute the spatially or momentum
resolved excitation spectra. In classical superconductors, where the phase
transition is related to formation of the Cooper pairs almost simultaneously
accompanied by onset of their long-range phase coherence, the Bogoliubov angle
is slanted all the way up to the critical temperature Tc. In the high
temperature superconductors and in superfluid ultracold fermion atoms near the
Feshbach resonance the situation is different because of the preformed pairs
which exist above Tc albeit loosing coherence due to the strong quantum
fluctuations. We discuss a generic temperature dependence of the Bogoliubov
angle in such pseudogap state indicating a novel, non-BCS behavior. For
quantitative analysis we use a two-component model describing the pairs
coexisting with single fermions and study their mutual feedback effects by the
selfconsistent procedure originating from the renormalization group approach.Comment: 4 pages, 4 figure