Rick Greene, Center for Nanophysics & Advanced Materials and Department of Physics, University of Maryland, College Park, MD 20742, USA

Jeudi 15 Septembre 2011, 16h00
Amphi Howleck, Esc C, 2ème etage

Link between spin fluctuations and Cooper pairing in copper oxide
superconductors

Rick Greene, Center for Nanophysics & Advanced Materials and Department of Physics, University of Maryland, College Park, MD 20742, USA

Although it is generally accepted that superconductivity (SC) is unconventional in the high transition temperature copper oxides (high-Tc cuprates), the relative importance of
phenomena such as spin and charge (stripe) order, SC fluctuations, proximity to a Mott
insulator, a pseudogap phase, and quantum criticality are still a matter of great debate. In
electron-doped cuprates, the absence of an anomalous pseudogap phase in the underdoped region of the phase diagram and weaker electron correlations, suggest that Mott physics and other unidentified competing orders are less relevant and that antiferromagnetic (AFM) spin fluctuations are the dominant feature. Here we demonstrate that a linear-temperature (T -linear) scattering rate - a key feature of the anomalous normal state properties of the cuprates - is correlated with the Cooper pairing. Through a study of
magnetotransport in thin films of the electron-doped cuprate La2-xCexCuO4 (LCCO), we
show that an envelope of T-linear scattering surrounds the SC phase, and survives to zero
temperature when superconductivity is suppressed by magnetic fields. Comparison with
similar behavior found in organic superconductors strongly suggests that the T-linear
resistivity is caused by spin-fluctuation scattering. A correlation between T-linear scattering and superconductivity has also been found in hole-doped cuprates.
Therefore, our results suggest a fundamental connection between AFM spin fluctuations and the pairing mechanism of high temperature superconductivity in all cuprates.

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