传统超导体中的电子配对发生在超导转变温度Tc,在电子态密度(DOS)中产生能隙D。在高温超导体中,在高于Tc的温度范围内,DOS中存在部分能隙。一个关键的问题是,在DOS以上的Tc的差距是否与配对,是什么决定了温度在不相干对的形式。在这里,我们报告的第一个空间分辨测量间隙形成的高Tc超导体,测量Bi 2Sr 2CaCu 2 O 8 +d样品具有不同的Tc值(空穴浓度为0.12至0.22),使用扫描隧道显微镜。在从0.16到0.22的掺杂范围内,我们发现配对间隙在Tc以上的纳米级区域中成核。这些区域随着温度的降低而扩散,导致超导状态下间隙尺寸的空间分布。尽管不均匀性,我们发现,每一个配对间隙的发展在温度Tp本地,以下的关系2D/kBTp = 8。在非常低的掺杂(<0.14)下,DOS的系统性变化表明存在另一种现象,该现象与电子配对无关,并且可能与电子配对竞争。我们对纳米级配对区域的观察为理解最近报道的空穴掺杂高Tc氧化铜超导体中Tc以上的波动超导响应提供了缺少的微观基础。
英文摘要:
Pairing of electrons in conventional superconductors occurs at the superconducting transition temperature Tc, creating an energy gap D in the electronic density of states (DOS). In the high-Tc superconductors, a partial gap in the DOS exists for a range of temperatures above Tc. A key question is whether the gap in the DOS above Tc is associated with pairing, and what determines the temperature at which incoherent pairs form. Here we report the first spatially resolved measurements of gap formation in a high-Tc superconductor, measured on Bi2Sr2CaCu2O8+d samples with different Tc values (hole concentration of 0.12 to 0.22) using scanning tunnelling microscopy. Over a wide range of doping from 0.16 to 0.22 we find that pairing gaps nucleate in nanoscale regions above Tc. These regions proliferate as the temperature is lowered, resulting in a spatial distribution of gap sizes in the superconducting state. Despite the inhomogeneity, we find that every pairing gap develops locally at a temperature Tp, following the relation 2D/kBTp = 8. At very low doping (<0.14), systematic changes in the DOS indicate the presence of another phenomenon, which is unrelated and perhaps competes with electron pairing. Our observation of nanometre-sized pairing regions provides the missing microscopic basis for understanding recent reports of fluctuating superconducting response above Tc in hole-doped high-Tc copper oxide superconductors.
Visualizing Pairing Symmetry in Nematic Superconductors using spin-polarized spectroscopy of magnetic impurities
本文研究了二维和三维超导体中磁性杂质诱导的Yu-Shiba-Rusinov共振态的自旋极化光谱性质:FeTe $_{0.55}$ Se $_{0.45}$(二维)和Cu $_x$ Bi $_2$ Se $_3$(三维)上生长的少层Bi $_2$ Te $_3$.我们着重讨论了对对称性与自旋极化光谱拓扑图之间的关系。我们使用$T$矩阵方法计算了二维和三维材料的自旋极化局域态密度(SP LDOS)和相应的傅里叶变换。不同的杂质取向和不同的SP LDOS的各种情况进行了研究。我们发现,像准粒子干涉谱,SP LDOS可以用来区分其他配对保持三重旋转对称性的$D_3$点群和在这些材料中的$D_3$配对。
Visualizing the $d$-vector in a nematic triplet superconductor
最近的实验表明,在掺杂的Bi $_2$ Se $_3$和在超导衬底上的Bi $_2$ Te $_3$薄膜中,有强有力的证据表明三重态超导电性,但对底层超导电性的拓扑结构至关重要的三重态的$d$矢量的方向有不同的识别。在这里,我们表明,$d$ -矢量可以直接可视化的扫描隧道测量:在subgap能量的$d$ -矢量是沿着领先的峰值波矢量的准粒子干涉图案的潜在杂质,和反直觉的延长的本地密度的状态分布的旋涡。这些结果为实验提供了有用的指导,而实验的结果反过来又会对配对对称性提出严格的约束。
Visualizing Vortex Cluster Dynamics in the Weak Type-II Superconductor CaSb$_2$
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory(斯坦福材料能源科学研究所,SLAC国家加速器实验室);Geballe Laboratory for Advanced Materials, Stanford University(斯坦福大学先进材料盖巴尔实验室);Stewart Blusson Quantum Matter Institute, University of British Columbia(不列颠哥伦比亚大学斯图尔特·布森量子物质研究所);Department of Physics and Astronomy, University of British Columbia(不列颠哥伦比亚大学物理与天文学系)
Visualizing Chiral Edge Modes in Twisted Cuprate Superconductors via Scanning-Probe Quantum Sensing
Georgia Institute of Technology(佐治亚理工学院);Harvard University(哈佛大学);National Institute for Materials Science(国立材料研究所);Brookhaven National Laboratory(布鲁克海文国家实验室);Argonne National Laboratory(阿贡国家实验室)
Visualizing the low-energy electronic structure of the triplet superconductor UTe$_2$ through quasiparticle interference
Harvard University(哈佛大学);Niels Bohr Institute, University of Copenhagen(哥本哈根大学尼尔斯·玻尔研究所);University of Maryland, College Park(马里兰大学帕克分校);National Institute of Standards and Technology(美国国家标准与技术研究院);Washington University in St. Louis(圣路易斯华盛顿大学);Canadian Institute for Advanced Research(加拿大高级研究院)
Bridging atomic and mesoscopic length scales with Replica Scanning Tunneling Microscopy: Visualizing the atomic lattice of UTe$_2$ and the atomic scale superconducting gap modulations of FeSe close to micron length scales
Universidad Autónoma de Madrid(马德里自治大学);Universidad del Rosario(罗萨里奥大学)
Anyon Bosonization of 2D Fermions and Single Boson Phase Diagram Implied from Experiment on Visualizing Pair Formation in Superconductor Bi_2Sr_2CaCu_2O_{8+δ}
Visualizing the interplay of dual electronic nematicities in kagome superconductors
University of Science and Technology of China(中国科学技术大学);Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences(中国科学院物理研究所北京凝聚态物理国家研究中心);CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences(中国科学院理论物理研究所理论物理国家重点实验室);Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China(中国科学技术大学微尺度物质科学国家研究中心);Hefei National Laboratory, University of Science and Technology of China(中国科学技术大学合肥国家实验室)
Visualizing the melting of the charge density wave in UTe2 by generation of pairs of topological defects with opposite winding
Institute for Condensed Matter Theory, University of Illinois(伊利诺伊大学凝聚态理论研究所);Maryland Quantum Materials Center, Department of Physics, University of Maryland(马里兰大学物理系马里兰量子材料中心);NIST Center for Neutron Research, National Institute of Standards and Technology(美国国家标准与技术研究院中子研究中心);Department of Physics, Washington University in St. Louis(圣路易斯华盛顿大学物理系);Canadian Institute for Advanced Research(加拿大高级研究院)
Atomically-flat, chemically-stable, superconducting epitaxial thin film of iron-based superconductor, cobalt-doped BaFe$_2$As$_2$
最近报道了诸如Co掺杂的SrFe $_2$ As $_2$(SrFe $_2$ As $_2$:Co)的Fe基超导体的外延生长,但是由于它们具有粗糙的表面并且通过与环境大气中的水蒸气的反应而分解,因此对于器件应用而言仍然具有不足的性能。本文报道了在700 ℃下生长的Co掺杂BaFe $_2$ As $_2$外延膜的超导转变起始温度为20 K。该转变比在SrFe $_2$ As $_2$:Co膜上观察到的转变更尖锐,这将源于它们改进的结晶度。这些薄膜还具有原子级平坦的表面,具有台阶和露台结构,并表现出抗水蒸气暴露的化学稳定性。
From Majorana theory of atomic autoionization to Feshbach resonances in high temperature superconductors
埃托雷·马约拉纳的论文《不完全P三重态理论》(Theory of incomplete P triplets)发表于1931年,重点讨论了选择规则在原子光谱中两个电子激发的非辐射衰变中的作用,涉及离散和连续通道之间的组态相互作用。这项工作是一个关键的一步,了解1935年的工作乌戈法诺的非对称线型的两个电子激发和1958年赫尔曼Feshbach文件的形状共振核散射所产生的配置之间的相互作用许多不同的散射通道。如今,费什巴赫共振在许多不同领域都引起了高度的科学兴趣,特别是对于超冷气体和高Tc超导性。
Sign reversing Hall effect in atomically thin high temperature superconductors
我们制作了范德华异质结器件,使用几个单位晶胞厚度的Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$的磁输运测量。原子级薄样品的超导转变温度和载流子密度可以保持接近大块样品。在大块样品中,霍尔电导率的符号被发现是相反的正常状态附近的转变温度,但随着样品的厚度减小的温度-磁场相图中的霍尔符号反转的区域急剧扩大。基于涡核中的过剩电荷密度和超导涨落的霍尔符号反转的定量分析表明,在二维极限下,原子级薄样品中存在重整化的超导能隙。