报告人简介：
吕佰晴，2018年于中国科学院物理研究所获得博士学位，2018至2022年在美国麻省理工学院从事博士后研究。2022年底加入上海交通大学李政道研究所任副教授。长期致力于凝聚态物理领域先进光电子能谱技术的研发和新奇量子态的研究。运用角分辨光电子能谱技术、X射线和电子衍射等多种技术手段，揭示了凝聚态物理中拓扑外尔电子态（入选2015年中国科学十大进展），三重简并费米子态（入选2017年中国科学十大进展）以及电荷密度波材料中非传统的热学回滞现象。其中外尔费米子实验发现成果还分别入选美国和英国物理学会评选的2015年国际物理学八大亮点和十大突破。以第一/通讯作者在Nature, Nat. Phys., PRX, PRL等期刊发表论文15篇，并在Nat. Rev. Phys.和 Rev. Mod. Phys.期刊上发表关于角分辨光电子能谱和拓扑半金属的长篇综述。
讲座摘要：
Recent advances in van der Waals heterostructures have opened the new frontier of moiré physics, whereby tuning the interlayer twist angle or adjusting lattice parameter mismatch have led to a plethora of exotic phenomena such as unconventional superconductivity and fractional quantum spin Hall effect. We extend the concept of moiré engineering to materials that host incommensurate orders, where we discovered a long-period, thermally-hysteretic moiré superlattice in a layered charge density wave (CDW) compound, EuTe4[1-4]. Using high-momentum-resolution X-ray diffraction performed on ultrathin flakes, we found two coexisting, incommensurate CDWs with slightly mismatched in-plane wavevectors. The interaction between these two CDWs leads to their joint commensuration with the high-symmetry lattice as well as a large moiré superstructure with an in-plane period of 13.6 nm, offering key insights into its unique properties, such as the stability of in-plane wavevectors [2] and the origin of in-gap states embedded in the rare semiconducting CDWs [3]. Due to different out-of-plane orders of the incommensurate CDWs, the moiré superstructure exhibits a clear thermal hysteresis, accounting for the large hysteresis observed in electrical resistivity and numerous metastable states induced by light or electrical pulses. Our findings pave the way for new developments in moiré engineering based on incommensurate lattices and highlight the important role of interlayer ordering in determining the macroscopic properties of these stacked structures.
主持人：蒋易凡，齐彦鹏
吕佰晴，2018年于中国科学院物理研究所获得博士学位，2018至2022年在美国麻省理工学院从事博士后研究。2022年底加入上海交通大学李政道研究所任副教授。长期致力于凝聚态物理领域先进光电子能谱技术的研发和新奇量子态的研究。运用角分辨光电子能谱技术、X射线和电子衍射等多种技术手段，揭示了凝聚态物理中拓扑外尔电子态（入选2015年中国科学十大进展），三重简并费米子态（入选2017年中国科学十大进展）以及电荷密度波材料中非传统的热学回滞现象。其中外尔费米子实验发现成果还分别入选美国和英国物理学会评选的2015年国际物理学八大亮点和十大突破。以第一/通讯作者在Nature, Nat. Phys., PRX, PRL等期刊发表论文15篇，并在Nat. Rev. Phys.和 Rev. Mod. Phys.期刊上发表关于角分辨光电子能谱和拓扑半金属的长篇综述。
讲座摘要：
Recent advances in van der Waals heterostructures have opened the new frontier of moiré physics, whereby tuning the interlayer twist angle or adjusting lattice parameter mismatch have led to a plethora of exotic phenomena such as unconventional superconductivity and fractional quantum spin Hall effect. We extend the concept of moiré engineering to materials that host incommensurate orders, where we discovered a long-period, thermally-hysteretic moiré superlattice in a layered charge density wave (CDW) compound, EuTe4[1-4]. Using high-momentum-resolution X-ray diffraction performed on ultrathin flakes, we found two coexisting, incommensurate CDWs with slightly mismatched in-plane wavevectors. The interaction between these two CDWs leads to their joint commensuration with the high-symmetry lattice as well as a large moiré superstructure with an in-plane period of 13.6 nm, offering key insights into its unique properties, such as the stability of in-plane wavevectors [2] and the origin of in-gap states embedded in the rare semiconducting CDWs [3]. Due to different out-of-plane orders of the incommensurate CDWs, the moiré superstructure exhibits a clear thermal hysteresis, accounting for the large hysteresis observed in electrical resistivity and numerous metastable states induced by light or electrical pulses. Our findings pave the way for new developments in moiré engineering based on incommensurate lattices and highlight the important role of interlayer ordering in determining the macroscopic properties of these stacked structures.
主持人：蒋易凡，齐彦鹏
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