标题： 电磁子、磁振子和声子在Eu$_{1-x}$Ho$_x$MnO$_3$ 显示英文标题

标题： Electromagnons, magnons, and phonons in Eu$_{1-x}$Ho$_x$MnO$_3$

摘要： 此处我们详细研究了混合钙钛矿锰氧化物系统Eu$_{1-x}$Ho$_x$MnO$_3$在钬浓度x=0.1和0.3时的太赫兹和远红外响应。 我们比较了四种不同的磁有序相（A型反铁磁、正弦调制的共线相、自旋平面垂直于晶体学a轴和c轴的螺旋相）的磁激发。 后两种相之间的转变伴随着铁电极化从P||a到P||c的切换。 特别关注了该转变处激发的温度依赖性。 我们发现强度有显著变化，表明交换应变机制不能是引起自旋波激发偶极权重的唯一机制。 我们还关注了非公度共线反铁磁相中的激发，并发现了一种迄今为止未观察到的接近40 cm$^{-1}$的激发。 对光学权重的详细分析给出了另一个意外结果：在P||c的多铁相中，所有电磁子的光谱权重都来自最低声子模。 然而，在P||a的相中，必须从更高频率转移额外的光谱权重。 显示英文摘要

摘要： Here we present a detailed study of the THz and FIR response of the mixed perovskite manganite system Eu$_{1-x}$Ho$_x$MnO$_3$ for holmium concentrations x = 0.1 and 0.3. We compare the magnetic excitations of the four different magnetically ordered phases (A-type antiferromagnetic, sinusoidally modulated collinear, helical phases with spin planes perpendicular to the crystallographic a and c axes). The transition between the two latter phases goes hand in hand with a switching of the ferroelectric polarization from P||a to P||c. Special emphasis is paid to the temperature dependence of the excitations at this transition. We find a significant change of intensity indicating that the exchange striction mechanism cannot be the only mechanism to induce dipolar weight to spin-wave excitations. We also focus on excitations within the incommensurate collinear antiferromagnetic phase and find a so far unobserved excitation close to 40 cm$^{-1}$. A detailed analysis of optical weight gives a further unexpected result: In the multiferroic phase with P||c all the spectral weight of the electromagnons comes from the lowest phonon mode. However, for the phase with the polarization P||a additional spectral weight must be transferred from higher frequencies.