Crossover from Localized Spins to Weak Coupling Charge Carriers: Theory for Nuclear Spin-Lattice Relaxation in Copper Oxide HTSC

Abstract

The dynamic spin susceptibility \(\chi^{+,-}_{\mathrm{total}}(\omega,{\bf q})\) that takes into account the interplay of localized and itinerant charge carriers exhibits a diffusive-like, extremely narrow and sharp symmetric ring of maxima at very small wave vectors: \(|{\bf q}|=q_{0}\) where q0∝ω/J≈10−6 with the Nuclear Magnetic Resonance (NMR) frequency ω and the superexchange coupling constant J together with the peak at the antiferromagnetic wave vector Q=(π,π). The calculated plane copper 63(1/T1) and oxygen 17(1/T1) nuclear spin-lattice relaxation rates from carrier-free right up to optimally doped La2−xSrxCuO4 are in good agreement with experimental data.