Determination of doped charge density in superconducting cuprates from NMR or stripes

Abstract

Independent investigations of nuclear quadrupole resonance (NQR) and of stripes in high-T c cuprates find a small deviation of doped-hole density h from the doping level of La 2−x Sr x CuO 4 .The value observed with NQR, x − h ≈ 0.02, agrees closely with the density of itinerant holes, p, responsible for suppression of 3D-AFM, as obtained from stripe incommensurability. The stripe model's assumption that doped holes in La 2−x Sr x CuO 4 reside at oxygen sites, and that doped electrons in Ln 2−x Ce x CuO 4 (Ln = P r, N d) reside at copper sites, is (to a large degree) confirmed with NQR. The NQR finding of doped-hole probabilities in oxygen and copper orbitals of HgBa 2 CuO 4+δ and other oxygen-enriched high-T c cuprates, P p P d 1/2, as well as of oxygendoped Y Ba 2 Cu 3 O 6+y , P p 2P d 2/3, is interpreted with the stripe model in terms of excess oxygen atoms in the CuO 2 planes and CuO chains.