Nuclear magnetic resonance measurement station in SECUF using hybrid superconducting magnets

Nuclear magnetic resonance(NMR) is one of the most powerful tools to explore new quantum states of condensed matter induced by high magnetic fields at a microscopic level. High magnetic field enhances the intensity of the NMR signal, and more importantly, can induce novel phenomena. In this article, examples are given on the field-induced charge density wave(CDW) in high-Tc superconductors and on the studies of quantum spin liquids. We provide a brief introduction to the high magnetic field NMR platform, the station 4 of the Synergetic Extreme Condition User Facility(SECUF), being built at Huairou, Beijing.     

钠钴氧超导体的核磁共振研究

文章介绍了利用核磁共振法对含水钠钴氧超导体研究的结果.实验表明,钠钴氧超导体的能隙函数存在线状节点,自旋单态配对.反铁磁自旋关联对超导的发生起重要作用.加水的主要效应是除了增加结晶结构的二维性外,还引发了反铁磁自旋关联.     

高温超导体的核磁共振研究

本文回顾了用核磁共振技术研究高温超导体的进展，着重介绍局域电荷分布，超导态性质以及赝能隙性质．除了CuO2面上的空穴密度总数外，Cu和O轨道上的空穴数的分布也是决定Tc的一个重要参数．核自旋晶格弛豫率以及奈特位移的实验结果显示，超导态的电子配对是d波单态配对．d波能隙函数里存在节点，使得准粒子从涡线中心“漏”到涡线外面．节点的存在也是非磁性杂质以及晶体无序会导致Tc明显降低的原因．45T高场下的实验发现，高温超导体的零温正常态是“费米弧”金属态．这说明赝能隙态和超导态是两个微观共存的物态．     

铁基超导体的量子临界行为

铁基超导体呈现丰富的电子相图, 各种有序态相互交叠. 本文主要介绍利用核磁共振手段在空穴型和电子型掺杂的BaFe₂As₂以及LaFeAsO_1-xF_x这三种具有代表性的铁基超导体中探测到的反铁磁序与超导序的微观共存、量子临界点和量子临界行为. 实验发现, 无论在空穴型还是电子型掺杂的铁基超导体中, 反铁磁相变温度都随着掺杂被抑制, 并最终在某个掺杂量降到零温而形成量子临界点. 在反铁磁转变温度之上存在结构相变, 其转变温度也随着掺杂而降低. 核磁共振谱证实结构相变也形成一个量子临界点. 本文介绍核磁共振及输运测量揭示的这两种量子临界点附近存在的量子临界行为, 共存态下奇异的超导性质等.     

ERBD+ENBD 治疗老年急性重症胆管炎疗效分析

急性重症胆管炎患者病情凶险，而老年患者机体耐受力差，如胆道引流不及时或无效，病死率较高。其救治原则首先是微创下的胆道通畅引流，目前首选是十二指肠镜（ERCP）下的胆管引流，主要操作包括：内镜下胆管外引流术（又称鼻胆管引流术，ENBD），内镜下胆管内引流术（又称胆道塑料支架引流术，ERBD），内镜下十二指肠乳头括约肌切开术（包括针形刀，EST）和取石。近年来，宁波市第九医院采用ERBD+ENBD成功救治老年急性重症胆管炎患者58例，取得了良好的效果，现报道如下。     

铁基高温超导体的超导能隙和自旋涨落:核磁共振研究

文章介绍了利用核磁共振法对铁基高温超导体的研究结果.笔者研究组断定铁基超导是自旋单态配对,并首先发现超导多能隙的存在.正常态的反铁磁自旋涨落在自旋空间是各向异性的,它与超导的关系,是人们关心的热点之一.     

Structural phase transition,precursory electronic anomaly,and strong-coupling superconductivity in quasi-skutterudite(Sr_(1-x)Ca_x)_3Ir_4Sn_(13) and Ca_3Rh_4Sn_(13)

The interplay between superconductivity and structural phase transition has attracted enormous interest in recent years. For example, in Fe-pnictide high temperature superconductors, quantum fluctuations in association with structural phase transition have been proposed to lead to many novel physical properties and even the superconductivity itself. Here we report a finding that the quasi-skutterudite superconductors(Sr_(1-x)Ca_x)_3Ir_4Sn_(13)(x = 0, 0.5, 1) and Ca_3Rh_4Sn_(13) show some unusual properties similar to the Fe-pnictides, through ~(119)Sn nuclear magnetic resonance(NMR) measurements. In(Sr_(1-x)Ca_x)_3Ir_4Sn_(13), the NMR linewidth increases below a temperature T*that is higher than the structural phase transition temperature Ts. The spin-lattice relaxation rate(1/T1) divided by temperature(T), 1/T1 T and the Knight shift K increase with decreasing T down to T*, but start to decrease below T*, and followed by more distinct changes at Ts. In contrast,none of the anomalies is observed in Ca_3Rh_4Sn_(13) that does not undergo a structural phase transition. The precursory phenomenon above the structural phase transition resembles that occurring in Fe-pnictides. In the superconducting state of Ca_3Ir_4Sn_(13), 1/T1 decays as exp(-?/kBT) with a large gap ? = 2.21 k_BT_c, yet without a Hebel–Slichter coherence peak, which indicates strong-coupling superconductivity. Our results provide new insight into the relationship between superconductivity and the electronic-structure change associated with structural phase transition.