Knight Sean, Prabhakaran Dharmalingam, Binek Christian, Schubert Mathias
Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588-0511, USA.
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.
Sci Rep. 2019 Feb 4;9(1):1353. doi: 10.1038/s41598-018-37639-8.
Here we present the use of Fabry-Pérot enhanced terahertz (THz) Mueller matrix ellipsometry to measure an electromagnon excitation in monoclinic cupric oxide (CuO). As a magnetically induced ferroelectric multiferroic, CuO exhibits coupling between electric and magnetic order. This gives rise to special quasiparticle excitations at THz frequencies called electromagnons. In order to measure the electromagnons in CuO, we exploit single-crystal CuO as a THz Fabry-Pérot cavity to resonantly enhance the excitation's signature. This enhancement technique enables the complex index of refraction to be extracted. We observe a peak in the absorption coefficient near 0.705 THz and 215 K, which corresponds to the electromagnon excitation. This absorption peak is observed along only one major polarizability axis in the monoclinic a-c plane. We show the excitation can be represented using the Lorentz oscillator model, and discuss how these Lorentz parameters evolve with temperature. Our findings are in excellent agreement with previous characterizations by THz time-domain spectroscopy (THz-TDS), which demonstrates the validity of this enhancement technique.
在此，我们展示了使用法布里 - 珀罗增强太赫兹（THz）穆勒矩阵椭圆偏振术来测量单斜晶系氧化铜（CuO）中的电磁子激发。作为一种磁致铁电多铁性材料，CuO表现出电序与磁序之间的耦合。这导致在太赫兹频率下产生特殊的准粒子激发，称为电磁子。为了测量CuO中的电磁子，我们利用单晶CuO作为太赫兹法布里 - 珀罗腔来共振增强激发的特征。这种增强技术能够提取复折射率。我们在0.705太赫兹和215 K附近观察到吸收系数的一个峰值，这对应于电磁子激发。这个吸收峰仅在单斜a - c平面中的一个主要极化轴上被观察到。我们表明该激发可以用洛伦兹振子模型来表示，并讨论这些洛伦兹参数如何随温度变化。我们的发现与先前通过太赫兹时域光谱（THz - TDS）进行的表征结果非常吻合，这证明了这种增强技术的有效性。
