铁基超导体 NaFe(1-x)Co(x)As 中各向异性准粒子干涉的掺杂依赖性。

Doping dependence of the anisotropic quasiparticle interference in NaFe(1-x)Co(x)As iron-based superconductors.

机构信息

State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China.

Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.

出版信息

Phys Rev Lett. 2014 Mar 28;112(12):127001. doi: 10.1103/PhysRevLett.112.127001. Epub 2014 Mar 24.

DOI:10.1103/PhysRevLett.112.127001

PMID:24724672

Abstract

We use scanning tunneling microscopy to investigate the doping dependence of quasiparticle interference (QPI) in NaFe1-xCoxAs iron-based superconductors. The goal is to study the relation between nematic fluctuations and Cooper pairing. In the parent and underdoped compounds, where fourfold rotational symmetry is broken macroscopically, the QPI patterns reveal strong rotational anisotropy. At optimal doping, however, the QPI patterns are always fourfold symmetric. We argue this implies small nematic susceptibility and, hence, insignificant nematic fluctuation in optimally doped iron pnictides. Since TC is the highest this suggests nematic fluctuation is not a prerequistite for strong Cooper pairing.

摘要

我们使用扫描隧道显微镜研究了 NaFe1-xCoxAs 铁基超导体中准粒子干涉（QPI）的掺杂依赖性。目的是研究向列涨落与库珀配对之间的关系。在母体和欠掺杂化合物中，宏观上打破了四重旋转对称性，QPI 图案显示出强烈的旋转各向异性。然而，在最佳掺杂下，QPI 图案总是四重对称的。我们认为这意味着向列态磁化率很小，因此在最佳掺杂的铁磷化物中向列涨落并不显著。由于 TC 是最高的，这表明向列涨落不是强库珀配对的先决条件。