Effects of field-induced hole-density modulation on normal-state and superconducting transport in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$

The hole-density dependence of the normal-state resistivity and transition temperature ${\mathit{T}}_{\mathit{c}}$ of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ was studied using the electric field effect in ultrathin films of 1 to 8 unit cells thickness. The change in resistivity was found to be equal to the field-induced variation in the areal carrier density, leading to a relation that the conductivity is proportional to the hole density. A similar linear dependence was also found in ${\mathit{T}}_{\mathit{c}}$. However, a saturation occurred in both cases but at different hole densities. The result reveals different effects of hole filling in influencing normal-state and superconducting transport of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$.