近日，美国哈佛大学的C. G. L. Bøttcher及其研究团队取得一项新进展。经过不懈努力，他们实现了超导体-铁磁体杂化双层中诱导双重各向异性配对的电路量子电动力学检测。相关研究成果已于2024年8月12日在国际知名学术期刊《自然—物理学》上发表。

本文介绍了一种探针，使研究人员能够利用源自电路量子电动力学的微波技术测量微米级超导体的超流密度。研究人员将此技术应用于超导体-铁磁体双层结构，发现由邻近效应诱导的超流密度在样品平面内呈现两重各向异性。同时，其还表现出幂律温度缩放特性，这表明其处于节点超导态。

这些实验结果与理论预测的具有节点p波序参量的诱导三重态配对的特征相符。此外，研究人员观察到在接近铁磁共振的频率下，微波响应发生变化，这表明铁磁层中的自旋动力学与诱导的超导序之间存在耦合。这项实验技术可广泛应用于更多场景，例如研究范德瓦尔斯异质结构等低维材料中的脆弱非传统超导性。

据悉，混合系统是非常规超导研究的前沿之一，是实现拓扑超导态的一个很有前景的平台。由于这些材料的介观尺寸，使用许多传统的测量技术来探测它们是具有挑战性的，因此需要新的实验探针才能成功地表征它们。

附：英文原文

Title: Circuit quantum electrodynamics detection of induced two-fold anisotropic pairing in a hybrid superconductor–ferromagnet bilayer

Author: Bttcher, C. G. L., Poniatowski, N. R., Grankin, A., Wesson, M. E., Yan, Z., Vool, U., Galitski, V. M., Yacoby, A.

Issue&Volume: 2024-08-12

Abstract: Hybrid systems represent one of the frontiers in the study of unconventional superconductivity and are a promising platform to realize topological superconducting states. These materials are challenging to probe using many conventional measurement techniques because of their mesoscopic dimensions, and therefore require new experimental probes so that they can be successfully characterized. Here, we demonstrate a probe that enables us to measure the superfluid density of micrometre-size superconductors using microwave techniques drawn from circuit quantum electrodynamics. We apply this technique to a superconductor–ferromagnet bilayer and find that the proximity-induced superfluid density is two-fold anisotropic within the plane of the sample. It also exhibits power-law temperature scaling that is indicative of a nodal superconducting state. These experimental results are consistent with the theoretically predicted signatures of induced triplet pairing with a nodal p-wave order parameter. Moreover, we observe modifications to the microwave response at frequencies near the ferromagnetic resonance, suggesting a coupling between the spin dynamics and induced superconducting order in the ferromagnetic layer. Our experimental technique can be employed more widely, for example to study fragile unconventional superconductivity in low-dimensional materials such as van der Waals heterostructures.

DOI: 10.1038/s41567-024-02613-x

Source: https://www.nature.com/articles/s41567-024-02613-x