Electron-spin excitation coupling in an electron-doped copper oxide superconductor

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High-temperature (high- Tc) superconductivity in the copper oxides arises from electron or hole doping of their antiferromagnetic (AF) insulating parent compounds. The evolution of the AF phase with doping and its spatial coexistence with superconductivity are governed by the nature of charge and spin correlations, which provides clues to the mechanism of high- Tc superconductivity. Here we use neutron scattering and scanning tunnelling spectroscopy (STS) to study the evolution of the bosonic excitations in electron-doped superconductor Pr0.88LaCe0.12CuO4−δ with different transition temperatures (Tc) obtained through the oxygen annealing process. We find that spin excitations detected by neutron scattering have two distinct modes that evolve with Tc in a remarkably similar fashion to the low-energy electron tunnelling modes detected by STS. These results demonstrate that antiferromagnetism and superconductivity compete locally and coexist spatially on nanometre length scales, and the dominant electron–boson coupling at low energies originates from the electron-spin excitations.

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Figure 1: Schematic diagram of polarized neutron scattering set-up and polarized neutron scattering data at various temperatures.
Figure 2: Energy dependence of SF and NSF scattering at Q=(1.5,−0.5,0) rlu for the 24 K PLCCO and χ′′(ω) in absolute units for the 21 and 24 K samples.
Figure 3: Comparison of the tunnelling spectra of the 21 and 24 K samples.
Figure 4: Spatial variation of gap and Bosonic modes.


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The neutron scattering work at UT/ORNL is supported by the US NSF-OISE-0968226, and by the US DOE, Division of Scientific User Facilities (P.D.). Work at BC is supported by US NSF-CAREER-0645299 (V.M.) and DOE DE-SC0002554 (Z.W.). The single crystal PLCCO growth effort at UT is supported by US DOE BES under Grant No. DE-FG02-05ER46202 (P.D.). Work at IOP is supported by the Chinese Academy of Sciences, the Ministry of Science and Technology of China (973 Project nos. 2010CB833102 and 2010CB923002). J.Z. is supported by a fellowship from Miller Institute of Basic Research in Science at Berkeley.

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P.D. and V.M. planned the neutron and STM experiments, respectively. J.Z., S.L., P.S., A.H., H.J.K., S.D.W. and P.D. carried out neutron scattering measurements and data analysis. F.C.N., S.K. and V.M. performed STM/STS measurements. The samples were grown by J.Z. and S.L. The paper was written by P.D., V.M. and Z.W. with input from J.Z., S.D.W., and F.C.N. All coauthors provided comments on the paper.

Correspondence to Pengcheng Dai or V. Madhavan.

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Zhao, J., Niestemski, F., Kunwar, S. et al. Electron-spin excitation coupling in an electron-doped copper oxide superconductor. Nature Phys 7, 719–724 (2011) doi:10.1038/nphys2006

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