论文标题
超导sr $ _ {14-x} $ ca $ _x $ _x $ cu $ _ {24} $ o $ $ $ _ {41} $
Valence Transition Theory of the Pressure-Induced Dimensionality Crossover in Superconducting Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$
论文作者
论文摘要
在发现超导率（SC）的三十年中，“正常”状态的性质和SC的机制仍然神秘。一种流行的理论方法是将CuO $ _2 $ layer视为耦合两腿一频哈伯德梯子。在未蛋白的两腿梯子中，旋转式旋转梯子占据了梯子，掺杂的梯子的特征是与准长范围顺序（quasi-lro）的超导相关性。 SR $ _ {14-X} $ ca $ _x $ cu $ _ {24} $ o $ $ _ {41} $（SCCO）中的压力诱导的SC在一个频段的阶梯理论中长期解释。来自准一到二维（1d到2D）的戏剧性压力驱动的交叉运输，以及由于SC先前的金属状态阶梯状态而导致的旋转间隙同时消失了自旋间隙，但是SC先于SC之前的梯子范围。最近的表明与距离阶梯的逼真的多频道模型中距离的超导相关性快速衰减为这种观点提供了额外的信誉。在这里，我们表明，梯子中压力驱动孔浓度增加的假设无法解释尺寸交叉。维度交叉是由于Cu-Ion离子性的离散变化所致，并伴随着孔从Cu转移到O-ION，导致“负电荷转移差距”。 SCCO中的价值转变驱动的维度交叉的理论提供了对孔和电子掺杂分层的丘比特的临界掺杂浓度的巨大电荷载体密度的一般性解释，我们提出了对我们理论的可伪造实验测试。
More than three decades after the discovery of superconductivity (SC) in the cuprates, the nature of the "normal" state and the mechanism of SC remain mysterious. One popular theoretical approach has been to treat the CuO$_2$ layer as coupled two-leg one-band Hubbard ladders. In the undoped two-leg ladder spin-singlets occupy ladder rungs, and doped ladders are characterized by superconducting correlations with quasi-long range order (quasi-LRO). Pressure-induced SC in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$ (SCCO) has long been explained within one-band ladder theories. The dramatic pressure-driven crossover from quasi one-to-two dimensional (1D-to-2D) transport and the simultaneous vanishing of the spin gap due to ladder singlets in the metallic state preceding SC however lie outside the scope of ladder-based theories. Recent demonstration of rapid decay of superconducting correlations with distance within a realistic multiband model of the cuprate ladder gives additional credence to this viewpoint. Here we show that the assumption of pressure-driven increase in hole concentration in the ladders cannot explain the dimensionality crossover. The dimensionality crossover is due to discrete change in Cu-ion ionicity accompanied by transfer of holes from the Cu to O-ions, leading to "negative charge-transfer gap". Our theory of valence transition driven dimensionality crossover in SCCO provides a generic explanation of the very large increase in charge carrier density at critical doping concentrations in both hole and electron doped layered cuprates We propose a falsifiable experimental test of our theory.
