Spin correlations of the electron-doped high transition-temperature superconductor Nd{2-x}Ce{x}CuO{4+/-delta}

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  • 15 September 2006
Abstract
High transition-temperature (Tc) superconductivity develops near antiferromagnetic phases, and it is possible that magnetic excitations contribute to the superconducting pairing mechanism. In order to assess the role of antiferromagnetism, it is essential to understand the doping and temperature dependence of the two-dimensional antiferromagnetic spin correlations. Here we report inelastic magnetic neutron scattering measurements on the electron-doped superconductor Nd{2-x}Ce{x}CuO{4\pm\delta}. The data demonstrate that long-range antiferromagnetism and superconductivity do not co-exist. Instead, there exists a magnetic quantum critical point where superconductivity first appears, consistent with an exotic quantum phase transition between the two phases [1]. Photoemission [2,3], optical spectroscopy [4,5], and charge transport [5] experiments have revealed pronounced charge anomalies below a characteristic 'pseudogap' temperature T*(x) associated with the opening of a partial gap of the electronic states along the Fermi surface. We demonstrate that the pseudogap in the electron-doped materials arises from a build-up of spin correlations, in agreement with recent theoretical proposals [6,7].

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