[en] Magneto-optical measurements of a quasi-one-dimensional (q1D) organic superconductor (DMET)₂I₃ has been performed by using a cavity perturbation technique. Several resonant absorption lines, which can be attributed to the q1D periodic orbit resonance (q1D POR), as well as the quite unusual high-order q1D POR coming from the corrugated Fermi surface (FS) in the interlayer direction were observed. Moreover, other harmonic resonances are also observed when the AC electric field is applied along the c*-axis. We will also show its estimated q1D FS from the data analysis where the estimated FS clearly shows why there is no spin-density-wave or charge-density-wave transition in (DMET)₂I₃ despite having a q1D FS

[en] The periodical oscillation of the Hall resistance as a function of the magnetic field (B) has been observed in the field-induced spin density wave (FISDW) state of (TMTSF)₂ClO₄in strong magnetic field [Uji et al. Phys. Rev. Lett. 94, 077206 (2005)]. The mechanism of this interesting phenomenon has not been explained. It is known that the periodic potential due to the ordering of the anion plays important role in the FISDWand the Hall conductivity. Although some properties such as the suppression of the FISDW state with even index are explained in the perturbative treatment of the periodic potential, the non-perturbative calculation is indispensable to this system because the periodic potential is thought to be not small. We calculate the susceptibility in the system to obtain the wave vector of the FISDW at strong fields. We also discuss the Hall resistance in the strong periodic potential case