Chiral superconductivity in heavy-fermion metal UTe2
Chiral superconductivity in heavy-fermion metal UTe2
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DOI：
10.1038/s41586-020-2122-2
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发表时间：
2020-03-01
期刊：
影响因子：
64.8
通讯作者：
Madhavan, Vidya
中科院分区：
文献类型：
--
作者：
Jiao, Lin;Howard, Sean;Madhavan, Vidya
扫描隧道显微镜和光谱测量显示重费米子超导体UTe 2的超导带隙内存在手征边缘态，表明存在手征自旋三重态超导体。自旋三重态超导体是自旋为1的电子对和奇宇称波函数的凝聚体（1）。三重态配对的一个有趣的表现是手性p波态，它在拓扑上是非平凡的，并为实现马约拉纳边缘模式提供了一个自然的平台（2，3）。然而，三重态配对在固态系统中是罕见的，迄今为止还没有在任何散装化合物中明确确定。考虑到配对通常是由铁磁自旋涨落介导的，含有f电子元素的铀基重费米子系统，可以同时具有强相关性和磁性，被认为是实现自旋三重态超导性的理想候选者（4）。在这里，我们介绍了最近发现的重费米子超导体UTe 2的扫描隧道显微镜研究，它的超导转变温度为1.6开尔文（5）。我们发现了共存的近藤效应和超导性的签名，显示竞争的空间调制内的一个单元格。在台阶边缘的扫描隧道光谱揭示了手性间隙状态的签名，这已被预测存在于拓扑超导体的边界。结合现有的数据表明三重态配对的UTe2，手性状态的存在表明，UTe2是一个强有力的候选人手性三重态拓扑超导性。
Scanning tunnelling microscopy and spectroscopy measurements show chiral edge states inside the superconducting gap of the heavy-fermion superconductor UTe2, indicating the presence of chiral spin-triplet superconductivity.Spin-triplet superconductors are condensates of electron pairs with spin 1 and an odd-parity wavefunction(1). An interesting manifestation of triplet pairing is the chiral p-wave state, which is topologically non-trivial and provides a natural platform for realizing Majorana edge modes(2,3). However, triplet pairing is rare in solid-state systems and has not been unambiguously identified in any bulk compound so far. Given that pairing is usually mediated by ferromagnetic spin fluctuations, uranium-based heavy-fermion systems containing f-electron elements, which can harbour both strong correlations and magnetism, are considered ideal candidates for realizing spin-triplet superconductivity(4). Here we present scanning tunnelling microscopy studies of the recently discovered heavy-fermion superconductor UTe2, which has a superconducting transition temperature of 1.6 kelvin(5). We find signatures of coexisting Kondo effect and superconductivity that show competing spatial modulations within one unit cell. Scanning tunnelling spectroscopy at step edges reveals signatures of chiral in-gap states, which have been predicted to exist at the boundaries of topological superconductors. Combined with existing data that indicate triplet pairing in UTe2, the presence of chiral states suggests that UTe2 is a strong candidate for chiral-triplet topological superconductivity.