Metal-Insulator Transition and Pseudogap in Bi$_{1.76}$Pb$_{0.35}$Sr$_{1.89}$CuO$_{6+\delta}$ High-$T_c$ Cuprates

摘要

It is inferred from bulk-sensitive muon Knight shift measurement for aBi$_{1.76}$Pb$_{0.35}$Sr$_{1.89}$CuO$_{6+\delta}$ single-layer cuprate thatmetal-insulator (MI) transition (in the low temperature limit, $T\rightarrow0$)occurs at the critical hole concentration $p=p_{\rm MI}=0.09(1)$, where theelectronic density of states (DOS) at the Fermi level is reduced to zero by thepseudogap irrespective of the N\'eel order or spin glass magnetism.Superconductivity also appears for $p>p_{\rm MI}$, suggesting that this featureis controlled by the MI transition. More interestingly, the magnitude of theDOS reduction induced by the pseudogap remains unchanged over a wide dopingrange ($0.1\le p\le0.2$), indicating that the pseudogap remains as a hallmarkof the MI transition for $p>p_{\rm MI}$.