Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi-Hubbard model

Kavli Affiliate: Feng Yuan

| First 5 Authors: Huaisong Zhao, Huaisong Zhao, , ,

| Summary:

The measurement of the pairing gap plays an essential role in studying the
physical properties of superconductors or superfluids. We develop a strategy
for measure the pairing gap through the dynamical excitations. With the random
phase approximation (RPA), the dynamical excitations of a two-dimensional
attractive Fermi-Hubbard model are studied by calculating the dynamical
structure factor. Two distinct collective modes are investigated: a Goldstone
phonon mode at the transferred momentum $bf q=left[0,0right]$ and a roton
mode at $bf q=left[pi,piright]$. The roton mode demonstrates a sharp
molecular peak in the low-energy regime. Remarkably, the area under the roton
molecular peak scales with the square of the pairing gap, which persists even
in three-dimensional and spin-orbit coupled (SOC) optical lattices. This result
provides a potential strategy to measure the pairing gap of lattice systems
experimentally by measuring the dynamical structure factor at $bf
q=left[pi,piright]$.

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