Shubnikov-de Haas effect and the fermi surface in an ambient-pressure organic superconductor[bis(ethylenedithiolo)tetrathiafulvalene]2Cu(NCS)2

Abstract

The Shubnikov-de Haas (SdH) effect has been observed in the recently discovered ambient-pressure organic superconductor ${\mathrm{}\left[\mathrm{b}\mathrm{i}\mathrm{s}\right(\mathrm{e}\mathrm{t}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{o}\mathrm{l}\mathrm{o}\left)\mathrm{t}\mathrm{e}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{a}\mathrm{f}\mathrm{u}\mathrm{l}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{e}\right]}_2$Cu${\mathrm{}\left(\mathrm{NCS}\right)\mathrm{}}_2$. This is the first unambiguous report on the SdH effect in organic compounds. The SdH signal is observed below 1 K, above 8 T, and at angles $\theta$ between the crystal $a^{*}$-axis and a magnetic field of less than 30°. The period $0.0015cos\theta \left({\mathrm{T}}^{-1\mathrm{}}\right)$ corresponds to the cylindrical closed Fermi surface obtained by the tight-binding method based on the extended Hückel approximation, which is critically dependent on the crystal symmetry. The temperature dependence of the oscillation amplitude gives the effective mass at the Fermi surface to be about $3.5m_0$.