Magnetic Properties of Quasi-One Dimensional Molecular Conductors

这是研究准一维分子导体TMTSF在低温和大磁场下的超导性、金属性和介电性的一个更新建议。上临界场对B=7T输运的最新研究。Rev. Lett. 78, 3555（1997）为非常规的自旋-三重态配对和新的场诱导维度交叉提供了强有力的证据。这些和类似的磁测量将扩展到更高的场，以寻找准一维超导体所预测的可重入超导性。在正常状态下，将研究一系列新的角磁阻振荡的起源，这些振荡映射了费米表面的曲率。将开始通过转矩磁强计寻找相应的角磁振荡。在介电状态下，“快速振荡”的起源将通过脉冲场中的转矩和输运研究到100T。这是一个在低温和大磁场下研究准一维分子导体TMTSF超导、金属和介电性能的更新建议。超导性是当两个带负电荷的电子相互吸引并成为“成对”时产生的，尽管事实是“异性相吸，同性相斥”。在所有常规超导体中，这些成对电子具有相反的自旋，使得这对电子的总自旋为零，这一事实在超导态的解释中起着重要作用。然而，最近的一项理论预测，在某些电子被限制主要朝一个方向运动的材料中，具有相同而不是相反自旋的电子可以形成对，并具有超导性。这种配对的一个结果是，磁场可以增强而不是破坏超导状态，从而开启了在非常高的磁场中再现超导性的有趣可能性。该项目涉及在一维分子导体中寻找高场超导性，其中最初的研究强烈地暗示了等自旋配对和可重入超导性。＊＊＊

97-01597 Naughton This is a renewal proposal to study superconducting, metallic and dielectric properties of the quasi-one dimensional molecular conductors TMTSF at low temperatures and large magnetic fields. Recent transport studies to B=7T of the upper critical field Phys. Rev. Lett. 78, 3555 (1997) provide strong evidence for unconventional spin-triplet pairing, and a novel field- induced dimensional crossover. These and similar magnetic measurements will be extended to higher fields in a search for reentrant superconductivity which has been predicted for such quasi-1- d superconductors. In the normal state, the origin of a new series of angular magnetoresistance oscillations, which map the curvature of the Fermi surface, will be investigated. A search for corresponding angular magnetic oscillations via torque magnetometry will be initiated. In the dielectric state, the origin of the "fast oscillations" will be investigated via torque and transport in pulsed fields to 100T. %%% This is a renewal proposal to study superconducting, metallic and dielectric properties of the quasi-one dimensional molecular conductors TMTSF at low temperatures and large magnetic fields Superconductivity arises when two negatively charged electrons become attracted to each other and become "paired", in spite of the fact that "opposites attract while likes repel". In all conventional superconductors, these paired electrons have opposite spin, such that the total spin of the pair is zero, a fact which plays an important role in the explanation of the superconducting state. A recent theory has predicted, however, that in certain materials in which electrons are confined to move mostly in one direction, electrons with the same, rather than opposite, spin, can form pairs, and superconduct. One consequence of this pairing would be that a magnetic field could enhance, rather than destroy , the superconducting state, opening the interesting possibility of superconductivity reappearing in very high magnetic fields. This project involves a search for high field superconductivity in a one- dimensional molecular conductor, where initial studies are strongly suggestive of equal spin pairing and reentrant superconductivity. ***