Metal-Insulator Transition in Copper Oxides Induced by Apex Displacements
Metal-Insulator Transition in Copper Oxides Induced by Apex Displacements
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DOI：
10.1103/physrevx.8.021038
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发表时间：
2018-05-10
影响因子：
12.5
通讯作者：
Van Schilfgaarde, Mark
中科院分区：
文献类型：
--
作者：
Acharya, Swagata;Weber, Cedric;Van Schilfgaarde, Mark
高温超导性已经在许多种由Cu和O平面构成的化合物中发现，这些平面被间隔层隔开。理解为什么临界温度如此之高一直是许多研究和广泛争议的主题。为了实现高温超导性，母体化合物要么是空穴掺杂的，例如La 2CuO 4（LCO）与Sr（LSCO），要么是电子掺杂的，例如Nd 2CuO 4（NCO）与Ce（NCCO）。在电子掺杂的铜氧化物中，反铁磁相比超导相更稳定。然而，最近发现，减少剩余的面外顶端氧显着影响相图，驱动这些化合物的超导相。在这里，我们使用一个最近开发的第一性原理方法来探讨如何位移的顶端氧（AO）在LCO的影响的光学间隙，自旋和电荷的可磁化率，和超导序参量。结合准粒子自洽GW（QS GW）和动力学平均场理论（DMFT），我们证明了LCO是一个Mott绝缘体。但是顶端氧的小位移通过定域-离域转变驱动化合物到金属态，在转变处伴随着d波序参量的最大值。我们解决的问题是否NCO可以被看作是LCO的极限与大的顶点位移，我们阐明了深层的物理原因，为什么NCO的行为是如此不同的空穴掺杂材料。我们揭示了最近观察到的Tc和电荷转移间隙之间的相关性，同时也提供了优化的高Tc超导体的设计指导。此外，我们的研究结果表明，强关联，足以诱导莫特间隙，可能不是高T-r超导的先决条件。
High temperature superconductivity has been found in many kinds of compounds built from planes of Cu and O, separated by spacer layers. Understanding why critical temperatures are so high has been the subject of numerous investigations and extensive controversy. To realize high temperature superconductivity, parent compounds are either hole doped, such as La2CuO4 (LCO) with Sr (LSCO), or electron doped, such as Nd2CuO4 (NCO) with Ce (NCCO). In the electron-doped cuprates, the antiferromagnetic phase is much more robust than the superconducting phase. However, it was recently found that the reduction of residual out-of-plane apical oxygen dramatically affects the phase diagram, driving those compounds to a superconducting phase. Here we use a recently developed first-principles method to explore how displacement of the apical oxygen (AO) in LCO affects the optical gap, spin and charge susceptibilities, and superconducting order parameter. By combining quasiparticle self-consistent GW (QS GW) and dynamical mean-field theory (DMFT), we show that LCO is a Mott insulator. but small displacements of the apical oxygen drive the compound to a metallic state through a localization-delocalization transition, with a concomitant maximum in d-wave order parameter at the transition. We address the question of whether NCO can be seen as the limit of LCO with large apical displacements, and we elucidate the deep physical reasons why the behavior of NCO is so different from the hole-doped materials. We shed new light on the recent correlation observed between T-c and the charge transfer gap, while also providing a guide towards the design of optimized high-T-c superconductors. Further, our results suggest that strong correlation, enough to induce a Mott gap, may not be a prerequisite for high-T-r superconductivity.