Exchange interaction between the triplet exciton and the localized spin in copper-phthalocyanine.
Exchange interaction between the triplet exciton and the localized spin in copper-phthalocyanine.
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DOI：
10.1063/1.4881897
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发表时间：
2014-06
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影响因子：
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通讯作者：
Wei Wu
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文献类型：
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作者：
Wei Wu
有机分子中的三重态激子态可能由单重态激发和随后的系统间交叉产生。特别是对于带有自旋的分子，可以预期三重态激子与分子上的原始自旋之间的交换相互作用。在本文中，通过使用密度泛函理论，从第一原理研究了铜酞菁（CuPc，自旋-1/2）中的这种交换相互作用，方法是使用交换相关性的各种近似值（从局域密度近似到远程校正混合交换泛函）。计算出的交换相互作用的大小为 meV 量级，最小值（1.5 meV，铁磁）由远程校正混合交换函数 CAM-B3LYP 给出。因此，这种交换相互作用可以产生皮秒量级振荡周期的自旋相干性，这比 CuPc 中的三线态寿命（通常为数十纳秒）短得多。这意味着在三重态消失之前，有可能利用光学激发和系间窜越来实验性地操纵铜上的局域自旋。
Triplet excitonic state in the organic molecule may arise from a singlet excitation and the following inter-system crossing. Especially for a spin-bearing molecule, an exchange interaction between the triplet exciton and the original spin on the molecule can be expected. In this paper, such exchange interaction in copper-phthalocyanine (CuPc, spin-½) was investigated from first-principles by using density-functional theory within a variety of approximations to the exchange correlation, ranging from local-density approximation to long-range corrected hybrid-exchange functional. The magnitude of the computed exchange interaction is in the order of meV with the minimum value (1.5 meV, ferromagnetic) given by the long-range corrected hybrid-exchange functional CAM-B3LYP. This exchange interaction can therefore give rise to a spin coherence with an oscillation period in the order of picoseconds, which is much shorter than the triplet lifetime in CuPc (typically tens of nanoseconds). This implies that it might be possible to manipulate the localized spin on Cu experimentally using optical excitation and inter-system crossing well before the triplet state disappears.