悟道无穷 | Lunch Break 午间学术交流会第九期来咯~

第九期“Lunch break”将在冬至日举行，我们准备了热气腾腾的饺子，邀请大家边享美食，边交流学术。本期交流会邀请了王漱明教授课题组和李建新教授课题组以及丁剑平教授课题组的三位优秀博士研究生，讲述他们的科研经验与已取得的学术成果。参会者可以现场沉浸式地聆听科研大佬们的科研进程，欢迎大家踊跃参加！

活动信息

时间：

12月21日（周六）11：30-13：00

地点：

新教-405

嘉宾介绍

王漱明教授课题组 2019级硕博研究生

报告主题：Versatile Metaphotonic Spin-Orbit Interactions(超构光子学中的多元化自旋-轨道相互作用研究)

报告摘要：Light carries both spin and orbital angular momentum (AM), dictated by its polarization and spatial degrees of freedom. Lately, metasurfaces have recently enabled spatially inhomogeneous optical fields, profoundly enhancing and coupling these AM properties. In this talk, we explore versatile metaphotonic spin-orbit interactions (SOI) by firstly revealing how 3D polarization interference in non-paraxial light generates generalized spin-orbit AM conversion. By extending the Jones matrix and integrating local and global phase designs, we demonstrate the transformation of non-diffracting beams, such as converting circular Airy beams into Bessel beams. Furthermore, we showcase the creation of generalized vortex beams by encoding arbitrary intensity profiles into the azimuthal phase gradient of a metasurface, culminating in a total AM plate. In the realm of optomechanics, we present a multifunctional device capable of trapping and rotating nanoparticles. Additionally, deformable metasurfaces, termed "Metavehicles," introduce 2D planar movement without the need for tightly focused beams, heralding advancements in optical meta-manipulation. Lastly, by coupling honeycomb and triangular topological lattices into hybrid photonic integrated circuits, we achieve multi-dimensional localized modes at various frequencies and spins. These findings bridge fundamental metaphotonic SOI with practical applications, advancing on-chip optical devices and enabling innovative meta-manipulation techniques.

李建新教授课题组2019级硕博研究生

报告主题：Fractional magnetization plateau and spinon quantum spin Hall state in kagome antiferromagnets(笼目反铁磁体中的分数磁化平台和自旋子量子自旋霍尔态)

摘要：The kagome lattice is an exceptional platform for exploring novel many-body states, owing to its distinctive lattice and electron structures. Motivated by very recent experimental observations of the 1/9-magnetization plateaus in YCu3(OH)6+xBr3−x and YCu3(OD)6+xBr3−x, our study delves into the magnetic-field-induced phase transitions in the nearest-neighbor antiferromagnetic Heisenberg model on the kagome lattice using the variational Monte Carlo technique. We uncover a phase transition from a zero-field Dirac spin liquid to a field-induced magnetically disordered phase that exhibits the 1/9-magnetization plateau. Through a comprehensive analysis encompassing the magnetization distribution, spin correlations, chiral order parameter, topological entanglement entropy, ground-state degeneracy, Chern number, and excitation spectrum, we pinpoint the phase associated with this magnetization plateau as a chiral Z3 topological quantum spin liquid and elucidate its diverse physical properties. As the magnetic field increases further, we also obtain a 1/3-magnetization VBS state.

Besides, we construct a spinon quantum spin Hall state in kagome antiferromagnets with an additional Dzyaloshinskii-Moriya interaction. This state is a gapped QSL sharing the analogous physical properties with quantum spin Hall state. In term of the category of topological order, it is an Abelian double-semion topological order (doubled Chern-Simons state or CSL+CSL-) described by a sum of two topological quantum field theories with opposite chiralities, which is suggested in string-net model. 

丁剑平教授课题组2021级博士研究生

报告主题: Generation, Control, and Applications of Iso-Propagation Vortex Beams(涡旋光场等传输特性的调控及应用)

摘要：Since the early 1990s, vortex beams have garnered significant attention due to their potential in fields such as optical manipulation, communication, and quantum processing. However, the practical application of vortex beams is constrained by the expansion of the beam dependent on the Orbital Angular Momentum (OAM): as the OAM increases, the size and divergence angle of the beam also increase. This issue significantly limits their applications in areas such as spatial mode multiplexing communication, fiber-optic data transmission, and micromanipulation. For instance, in optical communications, while vortex beams theoretically possessing OAM could provide an infinite number of orthogonal channels with immense data transmission potential, the increase in transmission size and divergence angle due to higher OAM orders leads to increased power loss at the receiver and more extensive mode crosstalk, thus severely limiting communication bandwidth. As a result, traditional vortex beams require the expansion of the receiver end to accommodate more channels, which significantly increases system complexity and cost, posing substantial challenges for practical communication systems. To overcome the OAM-dependent transmission behavior of traditional vortex beams, we have developed a new type of vortex carrier mode called Iso-propagation Vortex Beams. These beams exhibit transmission characteristics (transmission size and divergence angle) that are independent of the OAM order, effectively solving the limitation of traditional vortex beams diverging with OAM. We delved into the underlying causes of OAM-dependent divergence by examining energy flow dynamics and significantly improved the transmission robustness and efficiency of IPVBs through angular spectrum engineering. Moreover, we have explored and identified several promising applications for these beams, indicating their potential to optical manipulation and communication technologies.

参与方式

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（可点击文末阅读原文跳转）

https://table.nju.edu.cn/dtable/forms/0c1967ff-ee70-4257-b73f-97413c975819/