Spin fluctuations and the pseudogap in organic superconductors

Powell, B. J., Yusuf, Eddy and McKenzie, Ross H. (2009) Spin fluctuations and the pseudogap in organic superconductors. Physical Review B, 80 5: 054505.1-054505.7. doi:10.1103/PhysRevB.80.054505

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Author Powell, B. J.
Yusuf, Eddy
McKenzie, Ross H.
Title Spin fluctuations and the pseudogap in organic superconductors
Journal name Physical Review B   Check publisher's open access policy
ISSN 1098-0121
Publication date 2009-08-01
Year available 2009
Sub-type Article (original research)
DOI 10.1103/PhysRevB.80.054505
Open Access Status File (Publisher version)
Volume 80
Issue 5
Start page 054505.1
End page 054505.7
Total pages 7
Editor P. D. Adams
Place of publication College Park, MD, United States
Publisher American Physical Society
Language eng
Subject 970102 Expanding Knowledge in the Physical Sciences
0204 Condensed Matter Physics
Formatted abstract
We show that there are strong similarities in the spin-lattice relaxation of nonmagnetic organic chargetransfer salts and that these similarities can be understood in terms of spin fluctuations. Further, we show that, in all of the κ-phase organic superconductors for which there is nuclear-magnetic-resonance data, the energy scale for the spin fluctuations coincides with the energy scale for the pseudogap. This suggests that the pseudogap is caused by short-range spin correlations. In the weakly frustrated metals κ-(BEDT-TTF)2Cu[N(CN)2]Br, κ-(BEDT-TTF)2Cu(NCS)2, and κ-(BEDT-TTF)2Cu[N(CN)2]Cl (under pressure) the pseudogap opens at the same temperature as coherence emerges in the (intralayer) transport. We argue that this is because the spin correlations are cutoff by the loss of intralayer coherence at high temperatures. We discuss what might happen to these two energy scales at high pressures, where the electronic correlations are weaker. In these weakly frustrated materials the data is well described by the chemical pressure hypothesis (that anion substitution is equivalent to hydrostatic pressure). However, we find important differences in the metallic state of κ-(BEDT-TTF)2Cu2(CN)3, which is highly frustrated and displays a spin liquid-insulating phase. We also show that the characteristic temperature scale of the spin fluctuations in (TMTSF)2ClO4 is the same as superconducting critical temperature, which may be evidence that spin fluctuations mediate the superconductivity in the Bechgaard salts.
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Created: Wed, 07 Apr 2010, 02:05:07 EST by Jo Hughes on behalf of Physics