RESISTIVITY IN THE SPIN-GAP PHASE OF STRONGLY CORRELATED FERMIONS

In the gauge theories of strongly correlated electrons, the linear-T resistivity observed in high-temperature-superconductor cuprates is attributed to the scattering of charge carriers by low-frequency long-wavelength gauge fluctuations. We discuss the change in resistivity from the strange-metal to the spin-gap phase, where, in mean-field theory, the fermion liquid becomes superfluid, and its correlation with the change in nuclear relaxation rate T1. The effect of fluctuations is qualitatively described. We also discuss the low-temperature resistivity. Experimental data is not in disagreement with the gauge-fluctuation theory.