The quantum states in the strongly correlated electron systems

我的研究活动包括研究高温超导体的电子特性，以及研究海森堡自旋（磁）系统。高温超导体在足够高的温度下是很差的电导体，但当它们冷却到某个临界温度以下时就会成为超导体（导电而不损失能量），这取决于材料的化学成分。对于这些材料，我感兴趣的是了解它们的电子特性与普通金属（例如铜）之间存在的差异。这种理解可能有助于我们理解超导性和反铁磁性之间的相互作用，这是目前凝聚态物理学中最困难的问题之一。我在高温超导体的研究工作中使用了旋转磁的概念。更准确地说，旋转反铁磁性被用于模拟这些材料的赝隙行为。对于自旋系统，我寻找在所谓的反铁磁海森堡阶梯和层中实现的可能的自旋状态。这些态是自旋平均方向的非平凡排列。自旋排列取决于梯腿的数量，或者海森堡耦合层的层数，以及自旋-自旋耦合常数。此外，我对磁自由度和晶格自由度相互作用的结果状态很感兴趣。在一维自旋系统中，这种相互作用导致晶格的自旋-佩尔斯不稳定性。晶格参数和自旋耦合常数的二聚化导致了这种不稳定性。

My research activities consist of investigating the electronic properties of the high-temperature superconductors, and of studying the Heisenberg spin (magnetic) systems. High-temperature superconductors are poor electric conductors at high enough temperatures, but become superconductors (that conduct electricity without energy loss) when they are cooled below a certain critical temperature, which depends on the chemical composition of the material. For these materials, I am interested in understanding the differences that exist between their electronic properties and those of ordinary metals like copper for example. This understanding would likely help us understand the interplay between superconductivity and antiferromagnetism, which constitutes currently one of the most difficult issues of condensed matter physics. I use the concept of rotating magnetism in my research work on the high-temperature superconductors. More precisely, rotating antiferromagnetism is utilized in the modeling of the pseudogap behavior in these materials. For the spin systems, I look for the possible spin states that are realized in the so-called antiferromagnetic Heisenberg ladders and layers. These states are nontrivial arrangements of the spin average orientations. The spin arrangements depend on the number of legs in the ladders, or the number of layers in the Heisenberg coupled layers, and on the spin-spin coupling constant. Also, I am interested in the state that results form the interaction of the magnetic and lattice degrees of freedom. In the one-dimensional spin systems, this interaction leads to the spin-Peierls instability of the crystal lattice. A dimerization of the lattice parameter and the spin coupling constant results form this instability.