Non-fermi liquid behavior of the organic superconductor [formula omitted] probed by 13C-NMR

Abstract

We assessed 13C-NMR measurements in an organic salt, κ ‐ ( BEDT ‐ TTF ) 4 Hg 2.89 Br 8 , which exhibits superconductivity at 4.3 K under ambient pressure. We observed that ( T 1 T ) − 1 of H // and ⊥ layer at ambient pressure increased as the temperature was decreased to 7 K, but decreased further at lower temperatures, suggesting that the decrease of ( T 1 T ) − 1 was not due to the superconductive fluctuations, but due to the magnetism of the conduction electrons. Application of pressure suppresses ( T 1 T ) − 1 , with ( T 1 T ) − 1 becoming constant above 2 GPa. These results suggest that applying pressure alters the electron system from a non-Fermi liquid (NFL) to a Fermi liquid (FL) state and that antiferromagnetic fluctuations contribute to the origin of NFL behavior. Whereas most organic conductors show Fermi liquid behavior, this salt is an organic superconductor that shows NFL behavior due to the antiferromagnetic fluctuations.