平移不变系统中的Uhlmann数
Uhlmann number in translational invariant systems
摘要：
我们定义的Uhlmann数作为陈数的一个扩展，我们使用这个数量来描述的二维平移不变的费米系统在有限温度下的拓扑结构。我们考虑两个聚合系统，我们研究的变化，通过他们的拓扑结构的乌尔曼数。通过线性响应理论，我们将系统的两个几何量平均Uhlmann曲率和Uhlmann数分别与可直接测量的物理量即动态磁化率和动态电导率联系起来。
英文摘要：
We define the Uhlmann number as an extension of the Chern number, and we use this quantity to describe the topology of 2D translational invariant Fermionic systems at finite temperature. We consider two paradigmatic systems and we study the changes in their topology through the Uhlmann number. Through the linear response theory we linked two geometrical quantities of the system, the mean Uhlmann curvature and the Uhlmann number, to directly measurable physical quantities, i.e. the dynamical susceptibility and to the dynamical conductivity, respectively.
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