Oxygen was systematically incorporated in MBE grown MgB2 films using in-situ post-growth anneals in an oxygen environment. Connectivity analysis in combination with measurements of the critical temperature and resistivity indicate that oxygen is distributed both within and between the grains. High values of critical current densities in field (~4x10^5 A/cm^2 at 8 T and 4.2 K), extrabolated critical fields (>45 T) and slopes of critical field versus temperature (1.4 T/K) are observed. Our results suggest that low growth temperatures (300oC) and oxygen doping (>0.65%) can produce MgB2 with high Jc values in field and Hc2 for high-field magnet applications.
Superconductivity Induced in Iron Telluride Films by Low Temperature Oxygen Incorporation
我们报告的超导诱导膜的非超导，反铁磁母体材料FeTe的低温氧掺入在可逆的方式。X射线吸收表明，氧掺杂改变了名义Fe价态从2+在非超导状态，主要是3+在超导状态。因此，氧掺杂的FeTe中的超导性发生在与更常见的FeTe $_{1-x}$ Se $_x$完全不同的电荷和应变状态下。这项工作也提出了一个方便的路径进行掺杂实验原位与许多测量技术。
The effects of oxygen in spinel oxide Li1+xTi2-xO4-delta thin films
通过在样品制备过程中精确调节氧分压，研究了从超导LiTi_2 O_4-δ到绝缘Li_4 Ti_5 O_（12）薄膜的演变过程。在LiTi 2 O 4-delta超导薄膜中，随着氧分压的增加，氧空位被填充，c轴晶格常数逐渐减小。随着氧分压的增加，c轴晶格常数趋于稳定，Li 4 Ti 5 O 12相开始形成。充氧过程由扫描透射电子显微镜技术的角度明场图像显示。随着氧分压的增加，磁电阻温度的正负变化呈现出非单调的变化规律。本文还讨论了氧对LiTi_2 O_4-δ结构和超导电性影响的理论解释。
Impact of Oxygen Diffusion on Superconductivity in YBa$_2$Cu$_3$O$_{7-δ}$ Thin Films Studied by Positron Annihilation Spectroscopy
$_2$ O $_{7-δ}$（YBCO）中的氧缺陷$δ$对高温超导性起着至关重要的作用。本文利用电子正电子湮没线的多普勒展宽谱（符合谱）原位研究了生长在SrTiO $_3$（STO）衬底上的YBCO单晶薄膜中氧浓度及其深度分布的温度依赖性。发现回火过程中的氧扩散导致$δ$的明显深度依赖性，这是使用X射线衍射无法获得的。在几分钟内达到的稳态由表面处和与STO基底的界面处的氧交换限定。此外，我们揭示了深度依赖的临界温度$T_{\mathrm{c}}$在制备和回火的YBCO薄膜。
Stabilizing and Tuning Superconductivity in La$_3$Ni$_2$O$_{7-δ}$ Films: Oxygen Recycling Protocol Reveals Hole-Doping Analogue
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences（中国科学院上海高等研究院上海同步辐射光源）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Songshan Lake Materials Laboratory（松山湖材料实验室）
The phenomenon of oxygen incorporation induced superconductivity in iron telluride (Fe1+yTe, with antiferromagnetic (AFM) orders) is intriguing and quite different from the case of FeSe. Until now, the microscopic origin of the induced superconductivity and the role of oxygen are far from clear. Here, by combining in-situ scanning tunneling microscopy/spectroscopy (STM/STS) and x-ray photoemission spectroscopy (XPS) on oxygenated FeTe, we found physically adsorbed O2 molecules crystallized into c(2/3x2) structure as an oxygen overlayer at low temperature, which was vital for superconductivity.…
We used resonant elastic x-ray scattering at the Cu $L_3$ and Dy $M_5$ edges to investigate charge order in thin films of underdoped DyBa$_2$Cu$_3$O$_{6+x}$ (DyBCO) epitaxially grown on NdGaO$_3$ (110) substrates. The films show an orthorhombic crystal structure with short-range ortho-II oxygen order in the charge-reservoir layers. At the Dy $M_5$ edge we observe diffraction peaks with the same planar wavevectors as those of the two-dimensional charge density wave in the CuO$_2$ planes and of the ortho-II oxygen order, indicating the formation of induced ordered states on the rare-earth sublat…
In our recent work [Phys. Rev. Lett. 128, 137001 (2002)], we proposed that the apical oxygen vacancies act as anisotropic scattering impurities. Within the Born approximation, this leads to a quasi-particle scattering rate that is maximal (zero) in the antinodal (nodal) direction. This unique angular dependence provides a straightforward mechanism for some puzzling experimental results in overdoped La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) films regarding the superfluid density $ρ_s$ and optical conductivity $σ_1$. In a recent comment by H. U. Ozdemir et al. [arXiv:2206.01301], the importance of the natu…
Effect of varying material anisotropy on critical current anistropy in vicinal YBa$_2$Cu$_3$O$_{7-δ}$ thin films
高$T_{c}$铜氧化物超导体以其各向异性层状结构而闻名，某些材料确实趋向于Lawrence-Doniach超导体的极限。然而，YBa $_2$ Cu $_3$ O $_{7-δ}$具有比从其层间距预期的更小的各向异性。这是由于结构中的铜酸盐链。为了研究链氧对输运性质的影响，对完全氧化和脱氧的YBa $_2$ Cu $_3$ O $_{7-δ}$薄膜和最佳氧化的Y $_{0.75}$ Ca $_{0.2}$ Ba $_2$ Cu $_3$ O $_{7-δ}$薄膜进行了临界电流与外加场角的测量。在10个$^{\circ}$错切SrTiO $_3$衬底上生长薄膜，以观察到本征涡旋沟道效应。在依赖于场角的临界电流的研究中观察到的膜的涡旋沟道最小的形式被认为取决于膜氧化。涡流沟道效应取决于到弦-饼磁通线晶格的角相关交叉。所获得的结果似乎与Blatter等人的预测一致[Rev. Mod. Phys.，66（4）：1125（1994）]，增加的超导各向异性导致在较小的角度范围内存在扭结的弦-饼晶格。
There is a hot debate on the anomalous behavior of superfluid density $ρ_s$ in overdoped La$_{2-x}$Sr$_x$CuO$_4$ films in recent years. The linear drop of $ρ_s$ at low temperatures implies the superconductors are clean, but the linear scaling between $ρ_s$ (in the zero temperature limit) and the transition temperature $T_c$ is a hallmark of the dirty limit in the Bardeen-Cooper-Schrieffer (BCS) framework [I. Bozovic et al., Nature 536, 309 (2016)]. This dichotomy motivated exotic theories beyond the standard BCS theory. We show, however, that such a dichotomy can be reconciled naturally by the…
In our previously published work, we have reported colossal magnetoresistance, Andreev oscillations, ferromagnetism, and granular superconductivity in oxygen-implanted carbon fibers, graphite foils, and highly oriented pyrolytic graphite. In this follow-up research, more results on these oxygen-implanted graphite samples are presented. We show results from transport measurements on oxygen-implanted diamond-like carbon thin coatings, amorphous carbon films, and highly oriented pyrolytic graphite. Significantly, a three-order magnitude drop in the electrical resistance of the oxygen-implanted di…
Nickelate films have recently attracted broad attention due to the observation of superconductivity in the infinite layer phase of $Nd_{0.8}Sr_{0.2}NiO_2$ (obtained by reducing Sr doped $NdNiO_3$ films) and their similarity to the cuprates high temperature superconductors. Here we report on the observation of a new type of transport in oxygen poor $Nd_{0.8}Sr_{0.2}NiO_{3-δ}$ films. At high temperatures, variable range hopping is observed while at low temperatures a novel tunneling behavior is found where Josephson-like tunneling junction characteristic with serial resistance is revealed. We at…
