论文标题
在丘比特的伪库阶段，声子变成手性
Phonons become chiral in the pseudogap phase of cuprates
论文作者
论文摘要
丘比特的伪库相的性质仍然是一个主要难题。它的新签名之一是一个大型负热厅电导率$κ_ {\ rm xy} $，它看起来像偶数$ p $以下的pseudogap关键掺杂$ p^*$，但其起源尚不清楚。因为这个大$κ_ {\ rm xy} $即使在未固定的莫特绝缘子la $ _2 $ cuo $ _4 $中也观察到，它不能来自收费载体，这些定位在$ p = 0 $。在这里，我们表明，la $ _2 $ cuo $ _4 $的热量大厅电导率大致相同，与cuo $ _2 $ planes的热传输几乎相同，即$κ__ {\ rm zy}（t）（t）\ act）这表明大厅的响应必须来自声子，这些响应是唯一能够轻松地正常和平行地移动的热载体。在$ p> p> p^*$中，在两个la $ _ {\ rm 1.6-x} $ nd $ _ {\ rm 0.4} $ sr $ _x $ _x $ cuo $ _4 $ _4 $和la $ _ {\ rm 1.8-x 1.8-x} $ eu $ _ $ _ $ _ {\ rm $ $ $ $ $ $ _4 $ _4观察不观察C轴霍尔信号，即$κ_ {\ rm zy}（t）= 0 $，表明声子在伪随阶段之外的霍尔响应为零。声音厅的响应立即出现在$ p^* = 0.23 $以下，如大型$κ_ {\ rm zy}（t）$信号所证实的，我们在la $ _ {1.6-x} $ _ {1.6-x} $ nd $ _ {\ rm _ {\ rm 0.4} $ _x $ sr $ _x $ _x $ _x $ cuo $ _4 $ with $ p = 0.21 $ p = 0.21 $。声子在铜酸盐中变成手性的微观机制仍有待鉴定。该机制必须是固有的 - 从声子的耦合到其电子环境 - 而不是外部的，从结构性缺陷或杂质来看，因为$ p^*$的两侧都是相同的。这种固有的声子大厅效应为量子材料提供了一个新的窗口，它可以解释在其他拓扑非平凡的绝缘子中观察到的热厅信号。
The nature of the pseudogap phase of cuprates remains a major puzzle. One of its new signatures is a large negative thermal Hall conductivity $κ_{\rm xy}$, which appears for dopings $p$ below the pseudogap critical doping $p^*$, but whose origin is as yet unknown. Because this large $κ_{\rm xy}$ is observed even in the undoped Mott insulator La$_2$CuO$_4$, it cannot come from charge carriers, these being localized at $p = 0$. Here we show that the thermal Hall conductivity of La$_2$CuO$_4$ is roughly isotropic, being nearly the same for heat transport parallel and normal to the CuO$_2$ planes, i.e. $κ_{\rm zy}(T) \approx κ_{\rm xy} (T)$. This shows that the Hall response must come from phonons, these being the only heat carriers able to move as easily normal and parallel to the planes . At $p > p^*$, in both La$_{\rm 1.6-x}$Nd$_{\rm 0.4}$Sr$_x$CuO$_4$ and La$_{\rm 1.8-x}$Eu$_{\rm 0.2}$Sr$_x$CuO$_4$ with $p = 0.24$, we observe no c-axis Hall signal, i.e. $κ_{\rm zy}(T) = 0$, showing that phonons have zero Hall response outside the pseudogap phase. The phonon Hall response appears immediately below $p^* = 0.23$, as confirmed by the large $κ_{\rm zy}(T)$ signal we find in La$_{1.6-x}$Nd$_{\rm 0.4}$Sr$_x$CuO$_4$ with $p = 0.21$. The microscopic mechanism by which phonons become chiral in cuprates remains to be identified. This mechanism must be intrinsic - from a coupling of phonons to their electronic environment - rather than extrinsic, from structural defects or impurities, as these are the same on both sides of $p^*$. This intrinsic phonon Hall effect provides a new window on quantum materials and it may explain the thermal Hall signal observed in other topologically nontrivial insulators.
