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科学家发现伊辛超导体中的轨道FFLO态
作者:小柯机器人 发布时间:2023/5/30 13:33:21

近日,荷兰格罗宁根大学的Jianting Ye及其领导的研究小组取得一项新进展。经过不懈努力,他们发现了伊辛(Ising)超导体中的轨道Fulde-Ferrell-Larkin-Ovchinnikov(FFLO)态。相关研究成果已于2023年5月24日在国际权威学术期刊《自然》上发表。

该研究小组成功发现了多层伊辛超导体2H-NbSe2中的一种轨道FFLO态。输运测量结果表明,在该态中,平移和旋转对称性被破坏,这是有限动量库珀配对的典型特征。研究人员构建了完整的轨道FFLO相图,包括正常金属相、均匀的伊辛超导相和六重轨道FFLO态。这项研究突出了实现有限动量超导性的替代途径,并为在具有破缺反演对称性的类似材料中制备轨道FFLO态提供了一种普遍机制。

据悉,在同时具有时间和反演对称性的超导体中,外加磁场的塞曼效应可以破坏时间反演对称性,形成具有有限动量的传统Fulde–Ferrell–Larkin–Ovchinnikov (FFLO)态,其由具有有限动量的库珀对表征。在缺乏(局部)反演对称性的超导体中,塞曼效应仍可通过与自旋轨道耦合(SOC)相互作用而充当FFLO态的潜在机制。具体而言,塞曼效应与Rashba自旋轨道耦合(SOC)之间的相互作用可以导致形成更易获得的Rashba FFLO态,其在相图中覆盖更广泛的区域。然而,当因为伊辛型(Ising-type)自旋轨道耦合导致自旋被锁定而抑制了塞曼效应时,传统的FFLO场景将不再有效。相反地,通过将磁场的轨道效应与SOC相耦合,可以形成一种非常规的FFLO态,为具有破缺反演对称性的超导体提供了一种替代机制。

附:英文原文

Title: Orbital Fulde–Ferrell–Larkin–Ovchinnikov state in an Ising superconductor

Author: Wan, Puhua, Zheliuk, Oleksandr, Yuan, Noah F. Q., Peng, Xiaoli, Zhang, Le, Liang, Minpeng, Zeitler, Uli, Wiedmann, Steffen, Hussey, Nigel E., Palstra, Thomas T. M., Ye, Jianting

Issue&Volume: 2023-05-24

Abstract: In superconductors possessing both time and inversion symmetries, the Zeeman effect of an external magnetic field can break the time-reversal symmetry, forming a conventional Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state characterized by Cooper pairings with finite momentum1,2. In superconductors lacking (local) inversion symmetry, the Zeeman effect may still act as the underlying mechanism of FFLO states by interacting with spin–orbit coupling (SOC). Specifically, the interplay between the Zeeman effect and Rashba SOC can lead to the formation of more accessible Rashba FFLO states that cover broader regions in the phase diagram3,4,5. However, when the Zeeman effect is suppressed because of spin locking in the presence of Ising-type SOC, the conventional FFLO scenarios are no longer effective. Instead, an unconventional FFLO state is formed by coupling the orbital effect of magnetic fields with SOC, providing an alternative mechanism in superconductors with broken inversion symmetries6,7,8. Here we report the discovery of such an orbital FFLO state in the multilayer Ising superconductor 2H-NbSe2. Transport measurements show that the translational and rotational symmetries are broken in the orbital FFLO state, providing the hallmark signatures of finite-momentum Cooper pairings. We establish the entire orbital FFLO phase diagram, consisting of a normal metal, a uniform Ising superconducting phase and a six-fold orbital FFLO state. This study highlights an alternative route to achieving finite-momentum superconductivity and provides a universal mechanism to preparing orbital FFLO states in similar materials with broken inversion symmetries.

DOI: 10.1038/s41586-023-05967-z

Source: https://www.nature.com/articles/s41586-023-05967-z

期刊信息

Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/
投稿链接:http://www.nature.com/authors/submit_manuscript.html