Potassium-tetracyanoquinodimethane (K-TCNQ): A spin-Peierls system
Potassium-tetracyanoquinodimethane (K-TCNQ): A spin-Peierls system
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四氰基醌二甲烷钾 (K-TCNQ)：自旋 Peierls 系统
DOI：
10.1103/physrevb.18.3585
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发表时间：
1978
影响因子：
3.7
通讯作者：
V. Larochelle
中科院分区：
文献类型：
--
作者：
Y. Lépine;A. Caillé;V. Larochelle
分析了四氰基对苯醌二甲烷钾（K - TCNQ）的顺磁磁化率随温度的变化。K - TCNQ被认为处于哈伯德模型的强关联到中等关联区域。其磁性是根据局域自旋之间的海森堡交换哈密顿量来描述的。高温相的磁化率采用邦纳和费舍尔的海森堡均匀链理论进行拟合，由于沿堆叠轴的热膨胀，交换常数\(J\)是温度的函数。低温相采用非均匀海森堡链来描述，其具有一个与温度相关的序参量\(\delta(T)\)，该序参量具有像在自旋 - 派尔斯转变中那样的BCS依赖性。相变源于TCN\({\mathrm{Q}}^{-}\)阴离子的两种局部稳定的重叠模式之间复杂的位移结构变化，这种变化是由自旋 - 派尔斯类型的二聚化不稳定性驱动的。
The paramagnetic susceptibility of potassium-tetracyanoquinodimethane (K-TCNQ) as a function of temperature is analyzed. K-TCNQ is considered to be in the strong to intermediate correlation regime of the Hubbard model. The magnetic properties are described in terms of a Heisenberg exchange Hamiltonian between localized spins. The magnetic susceptibility of the high-temperature phase is fitted using the Heisenberg uniform-chain theory of Bonner and Fisher with an exchange constant $J$ which is temperature dependent as a result of the thermal expansion along the stacking axis. The low-temperature phase is described using a nonuniform Heisenberg chain with a temperature-dependent order parameter $\ensuremath{\delta}(T)$ having the BCS dependence as in the spin-Peierls transition. The phase transition comes from a complex displacive structural change between two locally stable overlapping modes of the TCN${\mathrm{Q}}^{\ensuremath{-}}$ anions which is driven by a dimerization instability of the spin-Peierls type.