Theory of phonon-assisted multimagnon optical absorption and bimagnon states in quantum antiferromagnets.
Theory of phonon-assisted multimagnon optical absorption and bimagnon states in quantum antiferromagnets.
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量子反铁磁体中声子辅助多磁振子光学吸收和双磁振子态理论。
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
Sawatzky
中科院分区：
文献类型：
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作者：
Lorenzana;Sawatzky
我们计算了类钙钛矿反铁磁体中声子辅助下的多磁振子红外吸收的有效电荷，并利用相互作用自旋波理论计算了双磁振子吸收的光谱。在任意磁振子对总动量的无规相位近似下，给出了两磁振子相互作用问题的完整方程组。自旋波理论的结果与最近在铜氧化物超导体的母体绝缘化合物中测量到的能带的主峰非常吻合。线的形状被解释为是由于吸收的一个声子加上一个新的准粒子激发的海森堡哈密顿量，包括一个长寿命的虚拟束缚态的两个磁振子（bimagnon）。在布里渊区的很大一部分中，双磁振子态具有明确的能量和动量。较高的能量带被解释为一个声子加上更高的多磁子吸收过程。提出了观测双磁子的其他可能的实验。此外，我们预测的线的形状为自旋-1系统La 2NiO 4。
We calculate the effective charge for multimagnon infrared absorption assisted by phonons in a perovskitelike antiferromagnet and we compute the spectra for two-magnon absorption using interacting spin-wave theory. The full set of equations for the interacting two-magnon problem is presented in the random-phase approximation for arbitrary total momentum of the magnon pair. The spin-wave theory results fit very well the primary peak of recent measured bands in the parent insulating compounds of cuprate superconductors. The line shape is explained as being due to the absorption of one phonon plus a new quasiparticle excitation of the Heisenberg Hamiltonian that consists of a long-lived virtual bound state of two magnons (bimagnon). The bimagnon states have well-defined energy and momentum in a substantial portion of the Brillouin zone. The higher-energy bands are explained as one phonon plus higher multimagnon absorption processes. Other possible experiments for observing bimagnons are proposed. In addition we predict the line shape for the spin-1 system La2NiO4.