近日，德国马克斯·普朗克物质结构与动力学研究所的A.Cavalleri&M.Buzzi及其研究团队取得一项新进展。经过不懈努力，他们揭示光驱动YBa₂Cu₃O_6.48中的磁场排出现象。相关研究成果已于2024年7月10日在国际权威学术期刊《自然》上发表。

该研究团队利用放置在样品周边的磁光材料中的法拉第旋转效应，深入探究了光驱动YBa₂Cu₃O_6.48晶体周围时变磁场的动态特性。研究人员在恒定的外加磁场和产生类似超导的光学特性的相同驱动条件下，观察到瞬态抗磁响应。此响应的幅度与同等形状和尺寸的典型II型超导体的预期响应相当，展现出约-0.3阶的体积磁化率χ_v。这个值与光诱导的无超导性的迁移率增加是不相容的。相反，它支持了赝隙相的概念，其中早期的超导相关性被驱动器增强或同步。

据悉，量子固体中的相干光驱动正在成为一个研究前沿，有许多有趣的非平衡量子相和瞬态光致功能现象的报道，如铁电性、磁性和超导性。在高温铜超导体中，某些声子模式的相干驱动导致了具有类似超导光学性质的瞬态，远远高于它们的转变温度T_c，并且贯穿赝隙相。然而，关于这种瞬态的微观性质以及如何将其与具有增强载流子迁移率的非超导状态区分开来的问题仍然存在。例如，目前尚不清楚在这种方式驱动的铜是否表现出迈斯纳抗磁性。

附：英文原文

Title: Magnetic field expulsion in optically driven YBa₂Cu₃O_6.48

Author: Fava, S., De Vecchi, G., Jotzu, G., Buzzi, M., Gebert, T., Liu, Y., Keimer, B., Cavalleri, A.

Issue&Volume: 2024-07-10

Abstract: Coherent optical driving in quantum solids is emerging as a research frontier, with many reports of interesting non-equilibrium quantum phases and transient photo-induced functional phenomena such as ferroelectricity, magnetism and superconductivity. In high-temperature cuprate superconductors, coherent driving of certain phonon modes has resulted in a transient state with superconducting-like optical properties, observed far above their transition temperature T_c and throughout the pseudogap phase. However, questions remain on the microscopic nature of this transient state and how to distinguish it from a non-superconducting state with enhanced carrier mobility. For example, it is not known whether cuprates driven in this fashion exhibit Meissner diamagnetism. Here we examine the time-dependent magnetic field surrounding an optically driven YBa₂Cu₃O_6.48 crystal by measuring Faraday rotation in a magneto-optic material placed in the vicinity of the sample. For a constant applied magnetic field and under the same driving conditions that result in superconducting-like optical properties, a transient diamagnetic response was observed. This response is comparable in size with that expected in an equilibrium type II superconductor of similar shape and size with a volume susceptibility χ_v of order -0.3. This value is incompatible with a photo-induced increase in mobility without superconductivity. Rather, it underscores the notion of a pseudogap phase in which incipient superconducting correlations are enhanced or synchronized by the drive.

DOI: 10.1038/s41586-024-07635-2

Source: https://www.nature.com/articles/s41586-024-07635-2