Spin electric effects in molecular antiferromagnets
Spin electric effects in molecular antiferromagnets
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DOI：
10.1103/physrevb.82.045429
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发表时间：
2010-07-28
影响因子：
3.7
通讯作者：
Loss, Daniel
中科院分区：
文献类型：
--
作者：
Trif, Mircea;Troiani, Filippo;Loss, Daniel
分子纳米磁体显示出明显的相干行为特征，并且具有多种有效的低能自旋哈密顿量，适合于编码量子比特和实现基于自旋的量子信息处理。在纳米尺度上，控制量子系统的首选机制是施加电场，电场很强，可以局部施加，并且开关迅速。在这项工作中，我们为识别适合于电子控制的分子纳米磁体提供了理论工具。通过群论对称性分析，我们发现三角形分子中的自旋-电子耦合是由交换相互作用的修正决定的，即使在没有自旋-轨道耦合的情况下也是可能的。在五角形分子中，只有在自旋-轨道相互作用存在的情况下，自旋-电子耦合才能存在。在磁中心，S=1/2自旋和S=3/2自旋都允许这种耦合。在Hubbard模型中，我们发现了自旋-电子耦合与分子中化学键的性质之间的关系，这表明强自旋-电子耦合的最佳候选者是具有接近简并的键轨道的分子。我们还研究了在核磁共振和电子自旋共振光谱以及在分子的磁化、电极化和比热的热力学测量中可能存在的自旋-电耦合的实验特征。
Molecular nanomagnets show clear signatures of coherent behavior and have a wide variety of effective low-energy spin Hamiltonians suitable for encoding qubits and implementing spin-based quantum information processing. At the nanoscale, the preferred mechanism for the control of a quantum systems is the application of electric fields, which are strong, can be locally applied, and rapidly switched. In this work, we provide the theoretical tools for identifying molecular nanomagnets suitable for electric control. By group-theoretical symmetry analysis we find that the spin-electric coupling in triangular molecules is governed by the modification of the exchange interaction and is possible even in the absence of spin-orbit coupling. In pentagonal molecules the spin-electric coupling can exist only in the presence of spin-orbit interaction. This kind of coupling is allowed for both s=1/2 and s=3/2 spins at the magnetic centers. Within the Hubbard model, we find a relation between the spin-electric coupling and the properties of the chemical bonds in a molecule, suggesting that the best candidates for strong spin-electric coupling are molecules with nearly degenerate bond orbitals. We also investigate the possible experimental signatures of spin-electric coupling in nuclear magnetic resonance and electron spin resonance spectroscopy, as well as in the thermodynamic measurements of magnetization, electric polarization, and specific heat of the molecules.