640 research outputs found
Tan contact and universal high momentum behavior of the fermion propagator in the BCS-BEC crossover
We derive the universal high momentum factorization of the fermion
self-energy in the BCS-BEC crossover of ultracold atoms using nonperturbative
quantum field theoretical methods. This property is then employed to compute
the Tan contact as a function of interaction strength, temperature, chemical
potential and Fermi momentum. We clarify the mechanism of the factorization
from an analysis of the self-consistent Schwinger-Dyson equation for the
fermion propagator, and compute the perturbative contact on the BCS and BEC
sides within this framework. A Functional Renormalization Group approach is
then put forward, which allows to determine the contact over the whole
crossover and, in particular, for the Unitary Fermi gas. We present numerical
results from an implementation of the Renormalization Group equations within a
basic truncation scheme.Comment: 19 pages, 11 figures, published versio
- …