Uniform hole doping in HgBa₂Ca₂Cu₃O_8+δ studied by ⁶³Cu NMR

We studied local magnetic properties of triple-CuÜ2-layer superconductors HgBa₂Ca₂Cu₃O_8+δ with rich ⁶³Cu isotope (underdoped T _c = 124 K and optimally doped T _c = 134 K) by ⁶³Cu NMR spin-echo techniques. The temperature dependences of the ⁶³Cu nuclear spin-lattice relaxation rate ⁶³(1/T ₁) and the spin Knight shift ⁶³K_spin of the inner plane Cu(1) site were nearly the same as those of the outer plane Cu(2) site in the normal states. The pseudogap temperature T* defined as the maximum temperature of ⁶³(1/T ₁ T) was 190 K for the underdoped T _c = 124 sample and 143 K for the optimally doped T _c = 134 K sample. The NMR results indicate the uniform hole distribution in the three layers, which is consistent with a coalescence of three-derived Fermi surfaces predicted by a band theory. The room temperature in-plane ${}^{63}{K}_{\text{spin}}^{ab}$ depends on whether the number of CuO₂ planes per unit cell is even or odd for the Hg-based multilayer cuprate superconductors. (paper)