在电子显微镜中探测（亚）纳米尺度的铁振子
Probing (sub)nanoscale ferrons in an electron microscope
- Arizona State University（亚利桑那州立大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用电子能量损失谱在钛酸铅中直接探测到（亚）纳米尺度的Higgs和赝Goldstone两类铁振子，发现其群速度显著高于软声子，且畴尺寸限制可使其加倍，为三维铁电体中的太赫兹应用开辟了新途径。
AI中文摘要：
铁振子是极化涨落的集体激发，由于传播距离长，可实现太赫兹通信和量子转换。尽管铁振子已在范德华铁电体和弛豫铁电体中得到实验验证，但在三维铁电体中尚无直接的（亚）纳米尺度实验证据。本文通过测量由极化涨落引起的振动信号，在钛酸铅中检测到（亚）纳米尺度的两类铁振子：Higgs模和赝Goldstone模。利用电子能量损失谱（EELS）中的动量转移，我们直接区分了软声子和铁振子。我们观察到Higgs模源于平行于极轴的软光学声子，而赝Goldstone模源于垂直于极化轴的软光学声子。结合朗道理论、拉曼光谱测量和EELS，我们发现体相极限下Higgs模的群速度是面外软声子的八倍，而赝Goldstone铁振子的群速度因长程偶极相互作用是面内软声子的六倍。我们进一步表明，畴尺寸限制效应导致相应的体相铁振子群速度加倍，达到约每秒15公里（几乎是面外软声子模式的15倍）。总体而言，本研究为在三维铁电体中探测铁振子开辟了途径，其中畴工程是太赫兹通信和转换的一个有前景的方向。
英文摘要：
Ferrons are collective excitations of polarization fluctuations that can enable terahertz communications and quantum transduction due to long propagation lengths. Although ferrons have been experimentally demonstrated in van der Waals ferroelectrics and relaxor ferroelectrics, there is no direct (sub)nanoscale experimental evidence of ferrons in three-dimensional ferroelectrics. Here, we detect two types of ferrons, Higgs and pseudo-Goldstone, at the (sub)nanoscale in lead titanate by measuring vibrational signals due to polarization fluctuations. By harnessing momentum transfer in electron energy loss spectroscopy (EELS), we directly distinguish between soft-phonons and ferrons. We observe that the Higgs mode originates from the soft optical phonon parallel to the polar axis, whereas the pseudo-Goldstone mode originates from the soft optical phonon perpendicular to the polarization axis. Together with Landau theory, Raman spectroscopy measurements, and EELS, we observe that Higgs group velocities, in the bulk limit, are eight times greater than those of out-of-plane soft phonons and the pseudo-Goldstone ferrons have group velocities six times greater than in-plane soft phonons due to long-range dipole interactions. We further show that the domain size confinement effects lead to doubling of the respective bulk ferron group velocities, reaching up to approximately 15 km per second (almost 15 times higher than the out-of-plane soft phonon modes). Overall, this study opens a pathway to the detection of ferrons in three-dimensional ferroelectrics with domain engineering as a promising avenue for terahertz communication and transduction.
