Unconventional symmetry-breaking phenomena due to nontrivial order parameters attract increasing attention in strongly correlated electron systems. Here, we predict theoretically the occurrence of nanoscale spontaneous spin current, called the spin-loop-current (sLC) order, as a promising origin of the pseudogap and electronic nematicity in cuprates. We reveal that the sLC is driven by the odd-parity electron-hole condensations that are mediated by transverse spin fluctuations around the pseudogap temperature $T^{*}$. At the same temperature, odd-parity magnon pair condensation occurs. The sLC order is “hidden” in that neither internal magnetic field nor charge-density modulation is induced, whereas the predicted sLC with finite wave-number naturally gives the Fermi arc structure. In addition, the fluctuations of sLC order work as attractive pairing interaction between adjacent hot spots, which enlarges the $d$-wave superconducting transition temperature $T_{\mathrm{c}}$. The sLC state will be a key ingredient in understanding the pseudogap, electronic nematicity, as well as superconductivity in cuprates and other strongly correlated metals.

中文翻译：

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铜和相关电子系统中的横向自旋波动介导的奇数奇偶自旋环电流阶

由于非平凡的阶次参数而引起的非常规对称破坏现象在高度相关的电子系统中引起了越来越多的关注。在这里，我们从理论上预测纳米级自发自旋电流（称为自旋环电流（sLC）阶）的出现，这是铜酸盐中伪间隙和电子向列性的有希望的起源。我们揭示了sLC是由伪奇偶温度附近的横向自旋波动介导的奇偶校验电子-空穴凝聚驱动的${Ť}^{*}$。在相同温度下，奇偶校验磁振子对发生凝结。sLC顺序是“隐藏的”，因为既不会感应内部磁场，也不会感应电荷密度调制，而预测的具有有限波数的sLC自然会给出费米弧结构。此外，sLC顺序的波动是相邻热点之间有吸引力的配对相互作用，从而扩大了$d$波超导转变温度 ${Ť}_{\mathrm{C}}$。sLC状态将是理解假间隙，电子向列性以及铜酸盐和其他高度相关金属中的超导性的关键因素。