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Why is the Tc So High in Fe-Based Pnictide and Chalcogenide Superconductors?

Published online by Cambridge University Press:  18 September 2014

Bing Lv ,
Liangzi Deng ,
Zheng Wu ,
Fengyan Wei ,
Kui Zhao ,
James K. Meen ,
Yu-Yi Xue ,
Li-Li Wang ,
Xu-Cun Ma  and
Qi-Kun Xue
...Show all authors
Bing Lv
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A.
Liangzi Deng
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A.
Zheng Wu
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A.
Fengyan Wei
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A.
Kui Zhao
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A.
James K. Meen
Affiliation:
TcSUH and Department of Chemistry, University of Houston, Houston, TX 77204-5003, U.S.A.
Yu-Yi Xue
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A.
Li-Li Wang
Affiliation:
Department of Physics, Tsinghua University, Beijing, China.
Xu-Cun Ma
Affiliation:
Department of Physics, Tsinghua University, Beijing, China.
Qi-Kun Xue
Affiliation:
Department of Physics, Tsinghua University, Beijing, China.
Ching-Wu Chu
Affiliation:
Texas Center for Superconductivity (TcSUH) and Department of Physics, University of Houston, Houston, TX 77204-5002, U.S.A. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
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Abstract

Recently, the detection of non-bulk superconductivity with unexpectedly high onset-Tcs up to 49 K in Pr-doped CaFe2As2 [(Ca,Pr)122] single crystals and the report of a Tc up to 65 K in one-unit-cell (1UC) FeSe epi-films, offer an unusual opportunity to seek an answer to the question posed in the title. Through systematic compositional, structural, resistive, and magnetic investigations on (Ca,Pr)122 single crystals, we have observed a doping-level-independent Tc, the simultaneous appearance of superparamagnetism and superconductivity, large magnetic anisotropy, and the existence of mesoscopic-2D structures in these crystals, thus providing clear evidence consistent with the proposed interface-enhanced Tc in these naturally occurring rareearth-doped Fe-based superconductors, (Ca,R)122. Similar resistive and magnetic measurements were also made on the 3–4UC FeSe ultrathin epi-films. We have detected weak links in the Meissner state below 20 K, weakly coupled small superconducting patches between 20–45 K, and collective excitations of spin and/or superconducting nature between 45–80 K. The unusual frequency dependences of the diamagnetic moment observed in the films in different temperature ranges will be presented and their implications discussed.

Keywords

superconductingFenanoscale
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1684: Symposium T – Superconductor Materials—From Basic Science to Novel Technology , 2014 , mrss14-1684-t04-01
Copyright
Copyright © Materials Research Society 2014 

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