近日，德国维尔茨堡大学的Laurens W. Molenkamp&Charles Gould及其研究团队取得一项新进展。经过不懈努力，他们对稀磁拓扑绝缘子基约瑟夫森结中的磁可调谐超电流进行研究。相关研究成果已于2024年4月1日在国际知名学术期刊《自然—物理学》上发表。

该研究团队成功证实，利用二维稀磁拓扑绝缘体(Hg,Mn)Te构建的约瑟夫森结能够诱导出Fulde-Ferrell-Larkin-Ovchinnikov态。这一发现是通过仔细观测临界电流对磁场和温度的依赖性得出的。Mn掺杂物的引入显著增强了塞曼效应，使得研究人员能够通过微小的外部磁场实现高精度的控制。

研究人员观察到临界电流在平面内磁场作用下的多重再入行为，他们将其归因于基态之间的相变，并伴随着π的相移。这一成果意味着在更为容易实现的实验条件下，研究人员可以对Fulde-Ferrell-Larkin-Ovchinnikov态进行深入研究。

据悉，当超导体处于自旋交换场的作用之下，其序参量会发生空间调制，这就是常说的Fulde-Ferrell-Larkin-Ovchinnikov态。通过调控约瑟夫森结器件中的自旋分裂场，人们可以诱导这种特殊状态的出现，进而探索更广泛的相图空间。

附：英文原文

Title: Magnetically tunable supercurrent in dilute magnetic topological insulator-based Josephson junctions

Author: Mandal, Pankaj, Mondal, Soumi, Stehno, Martin P., Ili, Stefan, Bergeret, F. Sebastian, Klapwijk, Teun M., Gould, Charles, Molenkamp, Laurens W.

Issue&Volume: 2024-04-01

Abstract: A superconductor, when exposed to a spin-exchange field, can exhibit spatial modulation of its order parameter, commonly referred to as the Fulde–Ferrell–Larkin–Ovchinnikov state. Such a state can be induced by controlling the spin-splitting field in Josephson junction devices, allowing access to a wide range of the phase diagram. Here we demonstrate that a Fulde–Ferrell–Larkin–Ovchinnikov state can be induced in Josephson junctions based on the two-dimensional dilute magnetic topological insulator (Hg,Mn)Te. We do this by observing the dependence of the critical current on the magnetic field and temperature. The substitution of Mn dopants induces an enhanced Zeeman effect, which can be controlled with high precision by using a small external magnetic field. We observe multiple re-entrant behaviours of the critical current as a response to an in-plane magnetic field, which we assign to transitions between ground states with a phase shifted by π. This will enable the study of the Fulde–Ferrell–Larkin–Ovchinnikov state in much more accessible experimental conditions.

DOI: 10.1038/s41567-024-02477-1

Source: https://www.nature.com/articles/s41567-024-02477-1