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首页> 外文期刊>Physica, B. Condensed Matter >Quantum phase transitions in magnetism and superconductivity: Emergent spin topology seen with neutrons
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Quantum phase transitions in magnetism and superconductivity: Emergent spin topology seen with neutrons

机译：磁性和超导性中的量子相变：中子观察到的自旋拓扑

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摘要

Magnetic spins and charges interact strongly in high-temperature superconductors. New physics emerges as layers of copper oxide are tuned towards the boundary of the superconducting (SC) phase. As the pseudogap increases the characteristic spin excitation energy decreases. We show that our well-annealed YBa2Cu3O6+x, (YBCO6+x) single crystals are orthorhombic and superconducting but not antiferromagnetically ordered. Near the critical concentration for superconductivity for x = 0.35 the spins fluctuate on two energy scales, one a relaxational spin response at similar to 2 meV and the other a slow central mode that is resolution-limited in energy (< 0.08 meV) but broad in momentum. The gradual formation on cooling of a central mode over a range of momenta suggests that the spin ground state from which coherent SC pairing emerges may be quantum disordered. We show that YBCO6.35 adopts a homogeneous state that consists of highly organized frozen sub-critical three-dimensional spin correlations. The continuous spin evolution indicates that a single quantum state occurs in contrast to claims from site-based probes that lightly doped YBCO undergoes a transition to antiferromagnetic (AF) Bragg order followed by a sharp transition to a cluster glass phase. For x = 0.35, where T-c = 18 K is reduced to 1/5 of T-cmax, the spin ground state is reached without a sharp transition and consists of short correlations extending over only 8 angstrom between cells and 42 angstrom within the planes. Polarized neutrons show the angular spin distribution to be isotropic unlike the AF insulator. Since moment is conserved we interpret this as evidence for hole-induced spin rotations rather than decay. Crown Copyright (c) 2006 Published by Elsevier B.V. All rights reserved.
机译：磁性自旋和电荷在高温超导体中强烈相互作用。随着氧化铜层向超导（SC）相边界的调整，出现了新的物理学方法。随着伪间隙的增加，特征自旋激发能降低。我们表明，经过充分退火的YBa2Cu3O6 + x（YBCO6 + x）单晶是正交晶且超导的，但没有反铁磁有序。在x = 0.35的超导临界浓度附近，自旋在两个能量尺度上波动，一个自旋弛豫响应类似于2 meV，另一个自旋是缓慢的中心模式，其能量受限于分辨率（<0.08 meV），但在动量。中心模在一定范围内的冷却过程中逐渐形成，这表明自发基态可产生量子无序，自旋基态会产生相干的SC配对。我们表明，YBCO6.35采用由高度组织的冻结亚临界三维自旋相关性组成的均匀状态。连续的自旋演化表明，与基于位点的探针所主张的相反，轻掺杂的YBCO经历了转变为反铁磁（AF）布拉格级的过程，然后急剧转变为团簇玻璃相。对于x = 0.35，其中T-c = 18 K减小为T-cmax的1/5，在没有急剧过渡的情况下达到了自旋基态，并且由短的相关性组成，这些相关性仅在单元之间延伸8埃，在平面内扩展到42埃。极化中子显示出与AF绝缘子不同的角度自旋分布是各向同性的。由于力矩是守恒的，因此我们将其解释为空穴引起的自旋旋转而不是衰减的证据。官方版权（c）2006，Elsevier B.V.保留所有权利。

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