Roton pair density wave in a strong-coupling kagome superconductor
Roton pair density wave in a strong-coupling kagome superconductor
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强耦合 Kagome 超导体中的旋子对密度波
DOI：
10.1038/s41586-021-03983-5
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发表时间：
2021-09-29
期刊：
影响因子：
64.8
通讯作者：
Gao, Hong-Jun
中科院分区：
文献类型：
--
作者：
Chen, Hui;Yang, Haitao;Gao, Hong-Jun
过渡金属kagome晶格材料具有物质的受抑、相关和拓扑量子态（1-9）。最近，发现了具有拓扑能带结构的钒基可果美金属的新家族AV（3）Sb（5）（A = K、Rb或Cs）（10，11）。这些层状化合物在低温下形成超导性之前被氧化并经历电荷密度波转变（11-19）。本文报道了用扫描隧道显微镜/光谱学和约瑟夫森扫描隧道光谱学在CsV_3Sb_5中观察到的非常规超导电性和对密度波（PDW）。我们发现CsV_3Sb_5具有V形的配对能隙Δ，其能量近似为0.5meV，是一个强耦合超导体（2 Δ/k（B）T（c）- 5），同时具有4a（0）单向和2a（0）× 2a（0）电荷序。值得注意的是，我们发现了一个3Q PDW伴随着双向的4a（0）/3空间调制的超导间隙，相干峰和隧道电导的间隙深度。我们将这种新的量子态称为与底层涡旋-反涡旋晶格相关的旋转PDW，它可以解释所观察到的电导调制。在外加磁场、抑制超导性的强场和Tc以上的零场中探测涡旋晕中的电子态，发现PDW是产生赝能隙和纠缠电子序的主要态。我们的研究结果显示出惊人的类比和区别的现象学的高T-c铜酸盐超导体，并提供基础，为理解相关的电子态和超导性的微观起源的钒基可果美金属。
The transition metal kagome lattice materials host frustrated, correlated and topological quantum states of matter(1-9). Recently, a new family of vanadium-based kagome metals, AV(3)Sb(5) (A = K, Rb or Cs), with topological band structures has been discovered(10,11). These layered compounds are nonmagnetic and undergo charge density wave transitions before developing superconductivity at low temperatures(11-19). Here we report the observation of unconventional superconductivity and a pair density wave (PDW) in CsV3Sb5 using scanning tunnelling microscope/spectroscopy and Josephson scanning tunnelling spectroscopy. We find that CsV3Sb5 exhibits a V-shaped pairing gap Delta similar to 0.5 meV and is a strong-coupling superconductor (2 Delta/k(B)T(c) - 5) that coexists with 4a(0) unidirectional and 2a(0) x 2a(0) charge order. Remarkably, we discover a 3Q PDW accompanied by bidirectional 4a(0)/3 spatial modulations of the superconducting gap, coherence peak and gap depth in the tunnelling conductance. We term this novel quantum state a roton PDW associated with an underlying vortex-antivortex lattice that can account for the observed conductance modulations. Probing the electronic states in the vortex halo in an applied magnetic field, in strong field that suppresses superconductivity and in zero field above T-c, reveals that the PDW is a primary state responsible for an emergent pseudogap and intertwined electronic order. Our findings show striking analogies and distinctions to the phenomenology of high-T-c cuprate superconductors, and provide groundwork for understanding the microscopic origin of correlated electronic states and superconductivity in vanadium-based kagome metals.