论文标题
临界温度和低能激发缺陷的自旋系统中
Critical temperature and low-energy excitations in gapped spin systems with defects
论文作者
论文摘要
从理论上讲，在三维和准低维系统的磁性和非磁杂质引起的磁有序相位，具有单位基态的单元基态与激发三胞胎状态的间隙隔开。利用渗透理论的思想，我们以较小的浓度$ n $的缺陷来估计过渡温度$ t_n（n）$，从而得出了低能基本激发状态的密度，并检查这些激励对特定热量和磁化的贡献。我们对$ t_n（n）$的表达方式以及特定的热量描述了在各种适当系统中获得的可用实验发现：旋转 - $ \ frac12 $二聚体材料，旋转剂化合物，旋转旋转体和Haldane链材料。但是，我们对$ t_n（n）$的表达与以前提出的许多不同。
We discuss theoretically the magnetically ordered phase induced by magnetic and nonmagnetic impurities in three-dimensional and quasi-low-dimensional systems with singlet ground states separated by a gap from excited triplet states. Using ideas of the percolation theory, we estimate the transition temperature $T_N(n)$ to the Néel phase at a small concentration $n$ of defects, derive the density of states of low-energy elementary excitations, and examine the contribution of these excitations to the specific heat and magnetization. Our expressions for $T_N(n)$ and for the specific heat describe well available experimental findings obtained in various appropriate systems: spin-$\frac12$ dimer materials, spin-ladder compounds, spin-Peierls and Haldane chain materials. However, our expression for $T_N(n)$ differs considerably from many of those proposed before.
