报告人：严鹏

报告题目：Twisted magnon frequency comb and Penrose superradiance

报告摘要：Quantization effects of the nonlinear magnon-vortex interaction in ferromagnetic nanodisks are studied. We show that the circular geometry twists the spin-wave fields with spiral phase dislocations carrying quantized orbital angular momentum (OAM). Meanwhile, the confluence and splitting scattering of twisted magnons off the gyrating vortex core (VC) generates a frequency comb consisting of discrete and equally spaced spectral lines, dubbed as twisted magnon frequency comb (tMFC). It is found that the mode spacing of the tMFC is equal to the gyration frequency of the VC and the OAM quantum numbers between adjacent spectral lines differ by one. By applying a magnetic field perpendicular to the plane of a thick nanodisk, we observe a magnonic Penrose superradiance inside the cone vortex state, which mimics the amplification of waves scattered from a rotating black hole. It is demonstrated that the higher-order modes of tMFC are significantly amplified while the lower-order ones are trapped within the VC gyrating orbit which manifests as the ergoregion. These results suggest a promising way to generate twisted magnons with large OAM and to drastically improve the flatness of the magnon comb.

报告简介： 严鹏，电子科技大学, 电子科学与工程学院(原微电子与固体电子学院), 校百人计划特聘教授。长期担任Physical Review Letters, Physical Review X, Physical Review Applied, Physical Review B, New Journal of Physics等国际学术期刊审稿人。 2015年担任国际磁学会议(IEEE Intermag)分会主席。2013年担任戈登会议"Spin Dynamics in Nanostructures"海报分会主席。 2012年担任德国雷根斯堡大学"热激发自旋电子学学术研讨会"大会组织者兼大会主席。德国科学基金会（DFG）优先项目"热激发自旋输运"指委会委员。研究方向为：自旋电子学 (Spintronics)与热激发自旋电子学 (Spin caloritronics), 自旋波 (Spin wave), 微磁学与磁动力学 (Magnetization dynamics), 腔量子电动力学 (Cavity quantum electrodynamics), 非平衡态热力学与统计 (Nonequilibrium thermodynamics and statistics), 生物磁性与磁导航(Biomagnetism and navigation) https://www.ese.uestc.edu.cn/info/5064/4824.htm