Spin-density wave in the vicinity of superconducting state in λ−(BETS)2GaBrxCl4−x probed by C13 NMR spectroscopy

This paper identifies the electronic state just close to the superconducting phase in a system of organic conductors lambda-(BETS)2GaBrxCl4-x as a spin-density-wave state, using nuclear magnetic resonance and resistivity measurements. This finding explains the unexplainable enhancement of spin fluctuation at low temperatures in lambda-(BETS)2GaCl4 and suggests that the superconductivity of lambda-type salts is mediated by spin-density-wave fluctuations.