论文标题
掺杂的ktao $ _3 $的电子 - 音波耦合的第一原理计算
First-principles calculation of electron-phonon coupling in doped KTaO$_3$
论文作者
论文摘要
由于最近在KTAO $ _3 $的表面上强烈地表面平面依赖性超导性的实验发现的动机，我们计算了掺杂的ktao $ _3 $的电子偶联强度（$λ$），$λ$，沿沿沿沿螺旋孔高度模对性的高度模拟指导。使用EPW软件包中实现的Wannier功能方法，我们在实验覆盖的掺杂范围内计算$λ$，并比较沿[001]，[110]和[111]相互空间方向的模式分辨分布。我们发现，在$γ$点附近的光学模式下，电子轴耦合最强，在[001]方向上有一定的分布到较高的$ k $值。与实验测量的临界温度的实验测量趋势相反，电子偶联强度随掺杂的函数在掺杂的函数上具有圆顶状的形状，并且其整合的总数在[001]方向上最大，并且在[111]方向上最小。这种分歧表明超导性的非BCS特征。取而代之的是，$λ$在$γ$左右的软光学模式中的强烈定位表明，铁电软模式波动的重要性，这得到了我们的发现，即模式分辨$λ$值在极性结构中得到了强烈增强。旋转轨道耦合的包含对我们计算的模式分辨的$λ$值的影响可以忽略不计。
Motivated by the recent experimental discovery of strongly surface-plane-dependent superconductivity at surfaces of KTaO$_3$ single crystals, we calculate the electron-phonon coupling strength, $λ$, of doped KTaO$_3$ along the reciprocal-space high-symmetry directions. Using the Wannier-function approach implemented in the EPW package, we calculate $λ$ across the experimentally covered doping range and compare its mode-resolved distribution along the [001], [110] and [111] reciprocal-space directions. We find that the electron-phonon coupling is strongest in the optical modes around the $Γ$ point, with some distribution to higher $k$ values in the [001] direction. The electron-phonon coupling strength as a function of doping has a dome-like shape in all three directions and its integrated total is largest in the [001] direction and smallest in the [111] direction, in contrast to the experimentally measured trends in critical temperatures. This disagreement points to a non-BCS character of the superconductivity. Instead, the strong localization of $λ$ in the soft optical modes around $Γ$ suggests an importance of ferroelectric soft-mode fluctuations, which is supported by our findings that the mode-resolved $λ$ values are strongly enhanced in polar structures. The inclusion of spin-orbit coupling has negligible influence on our calculated mode-resolved $λ$ values.
