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

Peng Cai; Wei Ruan; Xiaodong Zhou; Cun Ye; Aifeng Wang; Xianhui Chen; Dung-Hai Lee; Yayu Wang

doi:10.1103/PhysRevLett.112.127001

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

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

Authors

Peng Cai¹, Wei Ruan¹, Xiaodong Zhou¹, Cun Ye¹, Aifeng Wang², Xianhui Chen², Dung-Hai Lee³, Yayu Wang¹

Affiliations

¹ 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.
² 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.
³ Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA and Materials Science Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA.

PMID: 24724672
DOI: 10.1103/PhysRevLett.112.127001

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.