Quantum noise spectroscopy of superconducting dynamics in a cuprate thin film
Washington University（华盛顿大学）；University of California, Berkeley（加州大学伯克利分校）；Harvard University（哈佛大学）；Carnegie Mellon University（卡内基梅隆大学）；Texas Tech University（德克萨斯理工大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）
Zhongyuan Liu, Ruotian Gong, Jaewon Kim, Oriana K. Diessel, Jiajie Cheng, Qiaozhi Xu, Zackary Rehfuss, Xinyi Du, Guanghui He, Abhishek Singh, Yun Suk Eo, Erik A… 展开作者
Zhongyuan Liu, Ruotian Gong, Jaewon Kim, Oriana K. Diessel, Jiajie Cheng, Qiaozhi Xu, Zackary Rehfuss, Xinyi Du, Guanghui He, Abhishek Singh, Yun Suk Eo, Erik A. Henriksen, G. D. Gu, Norman Y. Yao, Francisco Machado, Sheng Ran, Shubhayu Chatterjee, Chong Zu
备注：
[Version 3] manuscript revision with additional experiments. 10 pages, 4 figures in main; 6 pages, 2 figures in methods; 16 pages, 15 figures in supplementary information. [Version 2] revised with methods and supplementary information. 9 pages, 4 figures in main; 4 pages, 2 figures in methods; 7 pages, 5 figures in supplementary information. [Original Version] 9 pages, 4 figures in main text
Characterizing the low-energy dynamics of quantum materials is crucial for understanding strongly correlated electronic states, yet remains experimentally challenging, particularly in two-dimensional systems. Here, we leverage nitrogen-vacancy (NV) centers in diamond as a non-invasive quantum sensor to study thin-film Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO), revealing several distinct dynamical phenomena across the superconducting phase diagram. At zero magnetic field and low temperatures, NV depolarization ($T_1$) spectroscopy captures GHz-scale noise from nodal quasiparticle excitations, consistent with Bardeen--Cooper--Schrieffer (BCS) mean-field theory. Near the critical temperature $T_c \approx 90$ K, supercurrent-fluctuation-induced noise sharply reduces $T_1$. By analyzing the temperature scaling of $T_1$, we observe clear deviations from mean-field prediction, reflecting the importance of order parameter fluctuations and enabling the determination of critical exponents. Under a small magnetic field, a broad and asymmetric reduction of $T_1$ unveils a liquid-like phase of mobile vortices. NV decoherence ($T_2$) spectroscopy further probes MHz-scale noise and reveals complex vortex-solid fluctuations well below $T_c$. Our results establish quantum noise spectroscopy as a non-invasive probe of superconducting dynamics over frequency and length scales complementary to existing techniques.
Spatially Selective and Reversible Doping Control in Cuprate Films
我们描述了一种可逆的，空间控制的铜氧化物薄膜掺杂方法。该技术已被用于创建超导体-反铁磁绝缘体-超导体（S-AFI-S）结和最佳掺杂超导体-欠掺杂超导体-最佳掺杂超导体（OS-US-OS）铜酸盐结构。我们演示了如何S-AFI-S结构可以用来可靠地测量在低温下使用超导体作为无缝电引线的反铁磁绝缘体区域的输运性质。我们还讨论了应用和基本的问题，可以解决与这种掺杂方法创建的结构。虽然在本工作中它是在铜氧化物膜（YBa 2Cu 3 O 7-δ）上实施的，但是该方法也可以应用于其物理性质由氧含量决定的任何混合价过渡金属氧化物。
Doping-dependent critical Cooper-pair momentum in thin, underdoped cuprate films
我们应用一个最近开发的低场技术感应测量的临界对动量$p_c$在薄，欠掺杂薄膜的Y $_{1-x}$钙$_{x}$钡$_{2}$铜$_{3}$ O $_{7-δ}$和Bi $_{2}$锶$_{2}$钙铜$_{2}$ O $_{8+δ}$反映了广泛的空穴掺杂。我们观察到，$p_c \propto \hbar/ξ$的规模与$T_c$，因此超流体密度$n_s(T\rightarrow0)$在我们的二维铜酸盐薄膜。这种关系是著名的预测与\textit{doping-independent}超导间隙的铜氧化物的通用模型，但尚未观察到的相干长度$ξ$的高场测量由于场诱导现象不包括在理论中。
Scanning tunneling spectroscopy study of c-axis proximity effect in epitaxial bilayer manganite/cuprate thin films
最近的实验研究表明，在由铁磁锰氧化物和超导铜氧化物组成的薄膜异质结构中存在着新的超导邻近效应。为了在显微镜下观察这种效应，我们对La $_{2/3}$ Ca $_{1/3}$ MnO $_3$ /YBa $_2$ Cu $_3$ O $_{7-δ}$（LCMO/YBCO）双层薄膜进行了扫描隧道光谱。采用脉冲激光烧蚀沉积法在SrTiO $_{3}$衬底上生长了不同厚度的$\emph{c}$轴取向薄膜。通过横截面透射电子显微镜证实了薄膜的异质外延性。在4.2 K下测量Tunnel光谱，并分析LCMO层上的配对间隙的签名。对于LCMO厚度小于5 nm的双层样品，观察到单层LCMO膜的不对称电导谱特征，没有明显的间隙结构。这些观察结果与涉及自旋单重态对的非常短距离的邻近效应一致，并且难以与涉及自旋三重态对的较长距离的邻近效应相协调。
Doping dependence of the vortex-core energy in bilayer films of cuprates
产生涡旋核所需的能量是解决欠掺杂铜酸盐中热涡旋波动物理学的基本成分。在这里，我们从理论上研究它的作用的发生Beresinskiii-Kosterlitz-无相变的双层膜的不均匀性。通过与Hetel等人[Nat.Phys.3，700（2007）]对Y $_{1-x}$ Ca $_{x}$ Ba $_{2}$ Cu $_{3}$ O $_{7-\d}$（YBCO）的两个晶胞薄膜中的穿透深度的最新测量的比较，我们可以提取涡旋芯能量$μ$的值，并且表明在低掺杂下$μ$与$T_c$线性地成比例。
1/8 Doping Anomalies and Oxygen Vacancies in Underdoped Superconducting Cuprates
讨论了几种铜氧化物超导体的热导率（$κ$）随温度和掺杂的变化。在YBa $_2$ Cu $_3$ O $_{6+x}$和Hg铜酸盐中观察到的1/8掺杂附近的正常状态$κ$和$κ$在$T_c$的斜率变化的抑制值，分别归因于局部晶格畸变和超导冷凝物的抑制。这两种现象都被认为是由局部平面孔的小区域引起的，可能是相分离的表现。结果表明，$κ$的相行为反映了条纹动力学和氧空位团簇对1/8掺杂异常条纹的钉扎。
