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arXiv 2201.11719cond-mat.supr-concond-mat.str-el
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与铜氧化物超导体中赝能隙坍塌相关的自旋涨落

Spin fluctuations associated with the collapse of the pseudogap in a cuprate superconductor

M. Zhu, D. J. Voneshen, S. Raymond, O. J. Lipscombe, C. C. Tam, S. M. Hayden

AI总结:

本研究针对铜氧化物超导体赝能隙坍塌处比热峰值对应的涨落性质不明的问题,通过非弹性中子散射观测到极低能集体自旋激发,揭示其与赝能隙坍塌及磁有序倾向的关联,解释了相关比热异常并为理解奇异金属行为提供线索。

摘要:

铜氧化物超导电性的起源理论依赖于对其表现出多种竞争序的正常态的理解。对La$_{2-x}$Sr$_x$CuO$_4$的输运和热力学测量显示,在赝能隙坍塌对应的掺杂浓度$p^{\boldsymbol{\u2c6c}}$附近,存在量子临界点的特征,包括电子比热$C$随掺杂$p$变化的峰值。与该峰值相关的涨落的基本性质尚不清楚。本文中,我们利用非弹性中子散射表明,在接近$T_c$且靠近$p^{\boldsymbol{\u2c6c}}$处,存在特征能量为$\u0127 Γ≈$5 meV的极低能集体自旋激发。冷却并施加8.8 T磁场会形成混合态,在10 meV以下具有更强的磁响应。我们得出结论,低能自旋涨落源于赝能隙的坍塌以及潜在的磁有序倾向。我们表明,$p^{\boldsymbol{\u2c6c}}$附近的大比热可以用集体自旋涨落来解释。我们测量到的自旋涨落存在于整个超导相图中,可能与过掺杂铜氧化物中观测到的奇异金属行为相关。

英文摘要:

Theories of the origin of superconductivity in cuprates are dependent on an understanding of their normal state which exhibits various competing orders. Transport and thermodynamic measurements on La$_{2-x}$Sr$_x$CuO$_4$ show signatures of a quantum critical point, including a peak in the electronic specific heat $C$ versus doping $p$, near the doping $p^{\star}$ where the pseudogap collapses. The fundamental nature of the fluctuations associated with this peak is unclear. Here we use inelastic neutron scattering to show that close to $T_c$ and near $p^{\star}$, there are very-low-energy collective spin excitations with characteristic energies $\hbar Γ\approx$~5 meV. Cooling and applying a 8.8~T magnetic field creates a mixed state with a stronger magnetic response below 10~meV. We conclude that the low-energy spin-fluctuations are due to the collapse of the pseudogap combined with an underlying tendency to magnetic order. We show that the large specific heat near $p^{\star}$ can be understood in terms of collective spin fluctuations. The spin fluctuations we measure exist across the superconducting phase diagram and may be related to the strange metal behaviour observed in overdoped cuprates.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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