Quantum spin correlations through the superconducting-to-normal phase transition in electron-doped superconducting Pr0.88LaCe0.12CuO4-delta.

The quantum spin fluctuations of the S = 1/2 Cu ions are important in determining the physical properties of high-transition-temperature (high T(c)) copper oxide superconductors, but their possible role in the electron pairing of superconductivity remains an open question. The principal feature of the spin fluctuations in optimally doped high-T(c) superconductors is a well defined magnetic resonance whose energy (E(R)) tracks T(c) (as the composition is varied) and whose intensity develops like an order parameter in the superconducting state. We show that the suppression of superconductivity and its associated condensation energy by a magnetic field in the electron-doped high-T(c) superconductor Pr(0.88)LaCe(0.12)CuO(4-delta) (T(c) = 24 K), is accompanied by the complete suppression of the resonance and the concomitant emergence of static antiferromagnetic order. Our results demonstrate that the resonance is intimately related to the superconducting condensation energy, and thus suggest that it plays a role in the electron pairing and superconductivity.