近日，浙江大学曹光旱及其研究小组与中国科学院物理研究所的程金光等人合作并取得一项新进展。经过不懈努力，他们揭示铬基笼目金属在压力下的超导性。相关研究成果已于2024年8月28日在国际权威学术期刊《自然》上发表。

本文报道了一种铬基笼目金属CsCr₃Sb₅的发现，其显著特征是具有强电子关联性、受阻磁性和接近费米能级的特征性扁平能带。在常压下，这种笼目金属在55K时发生结构和磁性相变，并伴有条纹状的4a₀结构调制。在高压下，相变演变为两个相变，可能与电荷密度波和反铁磁自旋密度波有序性有关。

这些类似密度波的有序性随压力逐渐受到抑制，值得注意的是，在3.65–8.0GPa的压力范围内出现了超导穹顶。当类似密度波的有序性在4.2GPa时完全被抑制时，超导转变温度达到最大值T_c^max=6.4K，且正常态表现出非费米液体行为，使人联想到铁基超导体中的非常规超导和量子临界性。这项研究工作为探究相关笼目体系中的超导性提供了一个前所未有的平台。

据悉，多年来，人们一直在理论上推测高度相关的笼目体系中存在超导性，然而实验上却难以实现。最近发现的钒基笼目材料既表现出超导性，又表现出电荷密度波有序性，但它们是非磁性的且相关性较弱。因此，这些材料不太可能具有理论上推测的奇异超导性。

附：英文原文

Title: Superconductivity under pressure in a chromium-based kagome metal

Author: Liu, Yi, Liu, Zi-Yi, Bao, Jin-Ke, Yang, Peng-Tao, Ji, Liang-Wen, Wu, Si-Qi, Shen, Qin-Xin, Luo, Jun, Yang, Jie, Liu, Ji-Yong, Xu, Chen-Chao, Yang, Wu-Zhang, Chai, Wan-Li, Lu, Jia-Yi, Liu, Chang-Chao, Wang, Bo-Sen, Jiang, Hao, Tao, Qian, Ren, Zhi, Xu, Xiao-Feng, Cao, Chao, Xu, Zhu-An, Zhou, Rui, Cheng, Jin-Guang, Cao, Guang-Han

Issue&Volume: 2024-08-28

Abstract: Superconductivity in a highly correlated kagome system has been theoretically proposed for years, yet the experimental realization is hard to achieve. The recently discovered vanadium-based kagome materials, which exhibit both superconductivity and charge-density-wave orders, are nonmagnetic and weakly correlated. Thus these materials are unlikely to host the exotic superconductivity theoretically proposed. Here we report the discovery of a chromium-based kagome metal, CsCr₃Sb₅, which is contrastingly featured with strong electron correlations, frustrated magnetism and characteristic flat bands close to the Fermi level. Under ambient pressure, this kagome metal undergoes a concurrent structural and magnetic phase transition at 55K, with a stripe-like 4a₀ structural modulation. At high pressure, the phase transition evolves into two transitions, possibly associated with charge-density-wave and antiferromagnetic spin-density-wave orderings. These density-wave-like orders are gradually suppressed with pressure and, remarkably, a superconducting dome emerges at 3.65–8.0GPa. The maximum of the superconducting transition temperature, T_c^max=6.4K, appears when the density-wave-like orders are completely suppressed at 4.2GPa, and the normal state exhibits a non-Fermi-liquid behaviour, reminiscent of unconventional superconductivity and quantum criticality in iron-based superconductors. Our work offers an unprecedented platform for investigating superconductivity in correlated kagome systems.

DOI: 10.1038/s41586-024-07761-x

Source: https://www.nature.com/articles/s41586-024-07761-x