论文标题
YBA $ _2 $ cu $ _4 $ o $ $ _8 $的伪随阶段内的单个单元内电子词内的微观证据
Microscopic evidence for the intra-unit-cell electronic nematicity inside the pseudogap phase in YBa$_2$Cu$_4$O$_8$
论文作者
论文摘要
了解神秘的伪随行现象的性质是与高$ T_C $超导体相关的最重要问题之一。在这里，我们报告了$^{17} $ o核磁共振（NMR）研究对化学计量库层中的两个平面氧站点yba $ _2 $ _2 $ cu $ _4 $ o $ $ _8 $，以调查伪造阶段内的对称性破坏。我们观察到，两个氧气位点的骑士移动在高温下是相同的，但低于$ t _ {\ rm nem} \ sim $ 185 k，它靠近pseudogap温度$ t^{\ ast} $。我们的结果为单位内电细胞电子词性提供了微观证据。两个氧位点之间四极共振频率的差异在$ t _ {\ rm nem} $以下没有变化，这表明观察到的nematicities并非直接源于局部电荷密度调制。此外，在低于$ t \ simeq $ 150 k的低于$^{17} $ o-o-o-nmr Spectra中的额外扩展是在$^{17} $ o-o-o-nmr Spectra中观察到的短距离电荷密度波（CDW）顺序，因为该CDW订单确定对于两个氧气位置不等，这与观察到的nematicity相似。这些结果表明nematicition，CDW顺序和伪群之间可能存在联系。
Understanding the nature of the mysterious pseudogap phenomenon is one of the most important issues associated with cuprate high-$T_c$ superconductors. Here, we report $^{17}$O nuclear magnetic resonance (NMR) studies on two planar oxygen sites in stoichiometric cuprate YBa$_2$Cu$_4$O$_8$ to investigate the symmetry breaking inside the pseudogap phase. We observe that the Knight shifts of the two oxygen sites are identical at high temperatures but different below $T_{\rm nem} \sim$ 185 K, which is close to the pseudogap temperature $T^{\ast}$. Our result provides a microscopic evidence for intra-unit-cell electronic nematicity. The difference in quadrupole resonance frequency between the two oxygen sites is unchanged below $T_{\rm nem}$, which suggests that the observed nematicity does not directly stem from the local charge density modulation. Furthermore, a short-range charge density wave (CDW) order is observed below $T \simeq$ 150 K. The additional broadening in the $^{17}$O-NMR spectra because of this CDW order is determined to be inequivalent for the two oxygen sites, which is similar to that observed in case of nematicity. These results suggest a possible connection between nematicity, CDW order, and pseudogap.
