Non-Fermi-liquid behavior of the organic superconductor κ-(BEDT-TTF)4Hg2.89Br8 probed by 13C NMR

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An organic salt, κ-(BEDT-TTF)4Hg2.89Br8 exhibits superconductivity at 4.3 K under ambient pressure suggesting non-Fermi-liquid (NFL) behavior just above Tc. Whereas most organic superconductors are controlled by the bandwidth in the half-filled electron system, this salt realizes a carrier doping away from the half-filled electron system as well as high-Tc cuprates. In order to investigate the origin of NFL behavior, we assessed 13C-NMR measurements in this salt and observed the antiferromagnetic fluctuation as same as in an organic antiferromagnet κ-(BEDT-TTF)2Cu[N(CN)2]Cl with the gap structure. Application of pressure suppresses (T1T)^[-1] and shifts its maximum to lower temperatures with (T1T)^[-1] becoming constant above 2 GPa. These results suggest that applying pressure alters the electron system from NFL to FL state and that antiferromagnetic fluctuations contribute to the origin of NFL behavior.
2010-06-21