Study of Strongly Correlated Electronic System of Low-Dimension in Organic Conductors

在（BEDT-TTF）_2KHg（SCN）_4及其族中，我们发现二维费米面的几何效应对磁电阻的影响。我们还发现了一个类似反铁磁的状态，推测是由于另一个一维费米面的不稳定性。在低于8 K的低温、低于23 T的弱磁场和低于5 Kbar的低压下发现了反铁磁态，在TMTSF盐中发现了磁电阻的另一种几何效应，并对场致自旋密度波的一些令人困惑的性质提出了解答.发现高场极限态的量子数为零。详细研究了DCNQI盐的重入跃迁。这类材料的电子性质可以用DCNQI分子堆π带的Peierls跃迁和铜离子引起的d带的Mott跃迁来理解，可以说低维性、电子关联、电子-声子相互作用和弱三维性等因素对这类材料的电子性质起着至关重要的作用。

The purpose of the present study is to clarify effects of the Coulomb correlation among electrons to properties of low-dimensional electronic system in organic conductors.In (BEDT-TTF)_2KHg(SCN)_4 and its family we found a geometrical effect of the two-dimensional Fermi surface to the magnetoresistance. We found also an antiferromagnetic-like state presumably due to instability of another Fermi surface of one-dimension. The anitiferromagnetic state was found to be present at low temperatures below 8 K, under weak magnetic fields below 23 T, and at low pressures below 5 Kbar.In TMTSF salts another geometrical effect to the magneto-resistance was found. In addition we presented answers to questions about puzzling properties of the field-induced spin density waves. The high-field limiting state was found to have the quantum number of zero.In DCNQI salts the reentrance transition was investigated in detail. Electronic properties of this class of materials were found to be understood in terms of the Peierls transition in the pi band of DCNQI molecular stacks and the Mott transition in the d band due to copper ions.In conclusion one can say that all factors of low-dimensionality, the electron correlation, the electron-phonon interaction, and weak three-dimensionality play essential roles in electronic properties of these materials.