In this letter, we investigate the fluctuation effects on the transport properties of unitary Fermi gases in the vicinity of the superfluid transition temperature $T_c$. Based on the time-dependent Ginzburg-Landau formalism of the BEC-BCS crossover,
we investigate both the residual resistivity below $T_c$ induced by phase slips and the paraconductivity above $T_c$ due to pair fluctuations. These two effects have been well studied in the weak coupling BCS superconductor, and here we generalize them to the unitary regime of ultracold Fermi gases. We find that while the residual resistivity below $T_c$ increases as one approaches the unitary limit, consistent with recent experiments, the paraconductivity exhibits non-monotonic behavior. Our results can be verified with the recently developed transport apparatus using mesoscopic channels.
The observation of quantum oscillations in underdoped cuprates has generated intense debate about the nature of the field-induced resistive state and its implications for the `normal state of high T_c superconductors. Quantum oscillations suggest an
underlying Fermi liquid state at high magnetic fields H and low temperatures, in contrast with the high-temperature, zero-field pseudogap state seen in spectroscopy. Recent heat capacity measurements show quantum oscillations together with a large and singular field-dependent suppression of the electronic density of states (DOS), which suggests a resistive state that is affected by the d-wave superconducting gap. We present a theoretical analysis of the electronic excitations in a vortex-liquid state, with short range pairing correlations in space and time, that is able to reconcile these seemingly contradictory observations. We show that phase fluctuations lead to large suppression of the DOS that goes like $sqrt{H}$ at low fields, in addition to quantum oscillations with a period determined by a Fermi surface reconstructed by a competing order parameter.
