摘要 :
By combining experimental measurements of the quasiparticle and dynamical magnetic properties of optimally electron-doped Pr_(0.88)LaCe_(0.12)CuO_4 with theoretical calculations, we demonstrate that the conventional fermiology app...
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By combining experimental measurements of the quasiparticle and dynamical magnetic properties of optimally electron-doped Pr_(0.88)LaCe_(0.12)CuO_4 with theoretical calculations, we demonstrate that the conventional fermiology approach cannot possibly account for the magnetic fluctuations in these materials. In particular, we perform tunneling experiments on the very same sample for which a dynamical magnetic resonance has been reported recently and use photoemission data by others on a similar sample to characterize the fermionic quasiparticle excitations in great detail. We subsequently use this information to calculate the magnetic response within the conventional fermiology framework as applied in a large body of work for the hole-doped superconductors to find a profound disagreement between the theoretical expectations and the measurements: this approach predicts a steplike feature rather than a sharp resonance peak, it underestimates the intensity of the resonance by an order of magnitude, it suggests an unreasonable temperature dependence of the resonance, and most severely, it predicts that most of the spectral weight resides in incommensurate wings which are a key feature of the hole-doped cuprates but have never been observed in the electron-doped counterparts. Our findings strongly suggest that the magnetic fluctuations reflect the quantum-mechanical competition between antiferromagnetic and superconducting orders.
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摘要 :
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 s...
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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-δ) (T_c = 24 K), is accompanied by the complete suppression of the resonance and the concomitant emergence of static antiferromag-netic 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.
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摘要 :
We use inelastic neutron scattering to probe magnetic excitations of an optimally electron-doped superconductor Nd_(1.85)Ce_(0.15)CuO_(4-δ) above and below its superconducting transition temperature T_c = 25 K. In addition to gra...
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We use inelastic neutron scattering to probe magnetic excitations of an optimally electron-doped superconductor Nd_(1.85)Ce_(0.15)CuO_(4-δ) above and below its superconducting transition temperature T_c = 25 K. In addition to gradually opening a spin pseudogap at the antiferromagnetic ordering wave vector Q = (1/2, 1/2,0), the effect of superconductivity is to form a resonance centered also at Q = (1/2, 1/2, 0) but at energies above the spin pseudogap. The intensity of the resonance develops like a superconducting order parameter, similar to those for hole-doped superconductors and electron-doped Pr_(0.88)LaCe_(0.12)CuO_4. The resonance is therefore a general phenomenon of cuprate superconductors, and must be fundamental to the mechanism of high-T_c superconductivity.
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