Unconventional low dimensional fluctuation in organic conductors

为了研究关联和涨落在低维有机导体中的作用，我们从理论上研究了基于玻色化的以下系统。(I)从绝缘体到金属的转变是在贝克加德盐的正常状态下的压力下发生的，显示出电荷间隙。这种转变由电荷间隙与链间跃迁的比率决定。用具有半填充带的两个耦合链研究了这一机制，其中一维涨落用重整化群方法处理。结果表明，当电荷间隙大于链间跃迁时，发生了禁闭。此外，还考察了从公度态开始的电子填充效应。(2)有机导体的自旋密度波在临界温度的1/3处出现新的相变。利用两个耦合链的位相哈密顿量，用传递积分方法研究了链间位相差的影响。结果表明，可公度能量和链间耦合的竞争导致了从公度态到非公度态的跃迁。(3)研究了两个耦合的无自旋链中杂质的影响，以了解链间跳跃在准一维系统中的作用。研究发现，当杂质的钉扎能大于相互作用引起的链间间隙时，发生一维局域化。除了上述结果，我们还研究了一维电子的电子态、自旋密度波的集体模以及杂质对自旋Peirls系统的影响。

We have studied theoretically the following system based on the bosonization in order to study a role of correlation and fluctuation in low dimensional organic conductors. (i) The transition from insulator to metal occurs under pressures in the normal state of Bechgaard salts, which exhibit the charge gap. Such a transition is determined by a ratio of the charge gap to the interchain hopping. The mechanism has been studied by use of two-coupled chains with a half-filled band, in which the one-dimensional fluctuation is treated in terms of the renormalization group method. It is demonstrated that the confinement occurs when the charge gap becomes larger than than the interchain hopping. Further the effect of the electron-filling from the commensurate state has been examined. (2) The spin density wave of organic conductors exhibits a novel transition at temperature of the 1/3 of the critical temperature. By using a phase Hamiltonian for two-coupled chains of SDW, the effect of the phase difference between chain has been investigated by use of the transfer integral method. It is shown that the competition between the commensurability energy and interchain coupling gives rise to the transition from the commensurate state to the incommensurate state. (3) The effect of impurity in two-coupled spinless chain has been studied to understand the role of interchain hopping in quasi-one-dimensional systems. It is found that the one-dimensional localization occurs when the pinning energy of impurity becomes larger than the interaction induced interchain gap. Besides the above results, we have examined the electronic state of one-dimensional electrons, collective modes of spin density wave and the impurity effect on spin Peirls system.