Magnetism and superconductivity in strongly correlated systems -- Magnétisme et supraconductivité dans des systèmes fortement corrélés

物理性质受粒子-粒子相互作用支配的材料称为强关联材料。这些相互作用在低温下产生了新的基态，其中超导电性和磁性是最重要的。这些态之间的竞争、共存和相互关系必须通过实验来研究，以了解它们在未来器件中的潜力。在这些材料中，具有低维特性的有机导体特别吸引人，因为非传统的超导态与磁性竞争。它们也被认为是理想的系统，因为在实验室中可以获得能量尺度(温度、压力、磁场)。超导薄膜也将被研究，这种薄膜可以更容易地被结合到同时显示磁性和电极化的新型器件和磁性材料(多铁性)中。我们建议在这些系统上进行超声和微波实验，以解决与识别和表征新型超导和/或磁态有关的重要问题。这样的实验对于支持构建这些材料的理论模型是必不可少的。这些实验将作为温度(低2-300K和超低20MK)、磁场(18特斯拉作为取向的函数)和静水压力(12Kbar)的函数来执行。这些测量可能构成完成我们对材料理解的关键实验。

Materials whose physical properties are dominated by particle-particle interactions are called strongly correlated. These interactions produce novel ground states at low temperatures among which superconductivity and magnetism are the most important. The competition, the coexistence and the interrelation between these states must be investigated experimentally to appreciate their potential in future devices. Among these materials, organic conductors with a low-dimensional character are particularly attractive because an unconventional superconducting state is in competition with magnetism. They are also considered as ideal systems because of energy scales (temperature, pressure, magnetic field) attainable in laboratories. Superconducting thin films which can be more easily incorporated in novel devices and magnetic materials showing simultaneously magnetism and electric polarization (multiferroics) will also be studied. We propose to perform ultrasonic and microwave experiments on these systems to address important issues related to the identification and characterization of the novel superconducting and/or magnetic states. Such experiments are essential to sustain the construction of theoretical models of these materials. These experiments will be performed as a function of temperature (low 2-300 K and ultra-low 20 mK), of magnetic field (18 Tesla as a function of orientation) and hydrostatic pressure (12 kbar). These measurements can potentially constitute key experiments to complete our understanding of the materials.