  In fermionic superfluids that are charge neutral, Nambu-Goldstone (NG) modes
also known as Anderson-Bogoliubov modes emerge as a result of spontaneous
symmetry breaking. Here, we discuss DC transport properties of such NG modes
through a quantum point contact. We show that contrary to a naive view that
enhancement of the phase stiffness may suppress transport of the NG modes,
there must be an anomalous contribution that survives at low temperature. This
contribution originates from the conversion process between the condensate and
NG mode. We find that within the BCS regime the anomalous contribution is
enhanced with increasing channel transmittance and attractive interaction, and
leads to a temperature-dependent Lorenz number and absence of the bunching
effect in current noise.
