报告摘要:

Kagome compounds provide a fertile playground to explore the rich interplay between geometry, topology and electronic correlations. In this talk, we focus on a topological kagome metal CsV₃Sb₅ which exhibits cascade of symmetry-breaking electronic phases, including charge density wave, electronic nematicity and superconductivity. A giant anomalous Hall conductivity is observed exactly following the CDW transition, and the superconductivity shows an unusual competition with this CDW state under pressure. These findings point to an unconventional nature of the CDW. Deeply in the CDW state, we found the emergence of electronic nematicity that intertwines with CDW and superconductivity, drawing strike parallel to the high temperature superconductors. A new CDW phase induced by pressure, evolving from the electronic nematicity in ambient-pressure triple-Q CDW state, is observed between P_c1 ~ 0.76 GPa and P_c2 ~ 2.02 GPa for the first time. Such new CDW, ascribed to a possible stripe-like CDW order with a unidirectional 4a₀ modulation, is likely to intertwine with superconductivity and leads to the two-dome feature of the superconducting phase. Meantime, we perform soft point-contact spectroscopy (SPCS) measurements in CsV₃Sb₅ to investigate the evolution of superconducting order parameter with pressure. Surprisingly, we find that the superconducting gap is significantly enhanced between the two SC domes. Moreover, the temperature dependence of the SC gap in this pressure range severely deviates from the conventional BCS behavior, evidencing for strong Cooper pair phase fluctuations. At low temperatures, the topological surface states cooperate with superconductivity, and Majorana zero modes can be realized inside the vortex cores. These findings reveal the complex intertwining of the stripe-like CDW with SC in the compressed CsV₃Sb₅, suggesting striking parallel to the cuprate superconductor La_2-xBa_xCuO₄. Our results point to the essential role of charge degree of freedom in the development of intertwining electronic orders, thus provides new constraints for theories. All these results establish CsV₃Sb₅ as an ideal playground to study the topology and correlation driven exotic electronic orders.

报告人简介：

陈仙辉，中国科学技术大学教授，中国科学院强耦合量子材料物理重点实验室主任。1992年在中国科学技术大学物理系获理学博士学位，曾先后作为洪堡基金学者在德国卡尔斯鲁厄研究中心和斯图加特马克斯·普朗克固体物理研究所工作，作为访问学者在日本北陆先端科学技术研究院、美国休斯敦大学德克萨斯超导研究中心和新加坡国立大学工作。陈仙辉长期从事超导和量子材料的探索及其物理研究，迄今已在《自然》（Nature）、《科学》（Science）等刊物发表SCI论文460余篇。曾获长江学者成就奖（2008）、求是杰出科技成就集体奖（2009）、国家自然科学奖一等奖（2013）、国际超导材料最高奖马蒂亚斯奖（Bernd T. Matthias Prize）（2015）、何梁何利基金科学与技术进步奖（2017）、发展中国家科学院（TWAS）物理学奖（2020）等。1998年获国家杰出青年科学基金资助，2002年入选教育部“长江学者奖励计划”特聘教授，2015年当选中国科学院院士。

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