Fe-vacancy ordering in superconducting K_1–xFe_2–ySe₂: First-principles calculations and Monte Carlo simulations

Journal Article · Mon Jul 20 00:00:00 EDT 2015 · Superconductor Science and Technology

DOI:https://doi.org/10.1088/0953-2048/28/9/095004· OSTI ID:1329680

Fang, Yong ^[1]; Tai, Yuan -Yen ^[2]; Deng, Junkai ^[1]; Wu, Chao ^[1]; Ding, Xiangdong ^[1]; Sun, Jun ^[1]; Salje, Ekhard K. H. ^[3]

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1. Xi'an Jiaotong Univ., Xi'an (China)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Xi'an Jiaotong Univ., Xi'an (China); Univ. of Cambridge, Cambridge (United Kingdom)

Fe vacancies in the 33 K superconductor K_1–xFe_2–ySe₂ show ordering schemes that may be correlated with its superconducting properties. First-principles calculations and kinetic Monte Carlo simulations lead to a very simple model for vacancy ordering. Repulsive dipolar interactions between Fe vacancies show three ground states: a $$\sqrt{8}\times \sqrt{10}$$ rhombus-ordered structure for 12.5% vacancies, a $$\sqrt{5}\times \sqrt{5}$$ squared lattice for 20% vacancies, and a $$\sqrt{5}\times \sqrt{5}$$ rhombus-ordered structure for 25% vacancies. Other structural states are derived from these three ground states and may contain additional disordered spatial regions. As a result, the repulsive interaction between Fe vacancies arises from enhanced Fe–Se covalent bonds, which differs from the well-known attractive interaction of Fe vacancies in body-centered cubic Fe.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1329680
• Report Number(s): LA-UR-15-23116
• Journal Information: Superconductor Science and Technology, Vol. 28, Issue 9; ISSN 0953-2048
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
material science