STM spectroscopy of (TMTSF)(2)PF6

The SDW phase of(TMTSF)(2)PF6 was investigated by the electron tunneling sp ectroscopy using a low temperature STM. At room temperature and 86 K, the t unneling conductance is almost flat indicating metallic state. Below T-SDW= 11.5 K, the spectrum shows the clear gap structure associated with the SDW state. The conductance curve is well explained by the mean field approximat ion for the quasi-one dimensional conductors. The SDW gap parameter Delta(S DW) and is an element of(0) which characterizes the transfer energy along t he b-axis, are estimated as Delta(SDW)=2.5-2.9 meV and is an element of(0)= 2.0-2.6 meV, respectively. The SDW-insulator-SDW tunneling spectrum was als o observed.