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Title: Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals

Abstract

Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe{sub 2}As{sub 2} (A = Ba, Sr) family (Fe-122). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} and Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, and the other with a V{sup 2/3} background conductance universally observed, extending even up to 100 meV for Sr{sub 0.6}Na{sub 0.4}Fe{sub 2}As{sub 2} and Sr(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}. The latter is also observed in point-contact junctions on the nonsuperconducting parent compound BaFe{sub 2}As{sub 2} and superconducting (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder-Tinkham-Klapwijk model, the data show a gap size of {approx} 3.0-4.0 meV with 2{Delta}{sub 0}/k{sub B}T{sub c} {approx} 2.0-2.6, consistent with the smaller gap size reported for the LnFeAsO family (Fe-1111). Formore » the Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, the G(V) curves typically display a zero-bias conductance peak.« less

Authors:
 [1];  [1];  [2];  [3];  [4];  [5];  [6];  [7];  [6];  [6];  [8];  [8];  [1]
  1. University of Illinois, Urbana-Champaign
  2. Zhejiang University
  3. Institute of Physics, Chinese Academy of Science
  4. Chinese Academy of Sciences
  5. Oak Ridge National Laboratory (ORNL)
  6. ORNL
  7. Louisiana State University
  8. Cambridge University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
988734
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Superconductor Science & Technology
Additional Journal Information:
Journal Volume: 23; Journal Issue: 5; Journal ID: ISSN 0953-2048
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; IRON ARSENIDES; BARIUM COMPOUNDS; STRONTIUM COMPOUNDS; ARSENIDES; MONOCRYSTALS; PNICTIDES; SPECTROSCOPY; SUPERCONDUCTORS; ENERGY GAP; POTASSIUM COMPOUNDS; COBALT ARSENIDES; ELECTRIC CONDUCTIVITY

Citation Formats

Lu, Xin, Park, W. K., Yuan, H. Q., Chen, G. F,, Luo, G. L., Wang, N. L., Sefat, A. S., McGuire, Michael A, Jin, R., Sales, Brian C, Mandrus, David, Gillett, J, Sebastian, Suchitra, and Greene, L. H. Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals. United States: N. p., 2010. Web. doi:10.1088/0953-2048/23/5/054009.
Lu, Xin, Park, W. K., Yuan, H. Q., Chen, G. F,, Luo, G. L., Wang, N. L., Sefat, A. S., McGuire, Michael A, Jin, R., Sales, Brian C, Mandrus, David, Gillett, J, Sebastian, Suchitra, & Greene, L. H. Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals. United States. https://doi.org/10.1088/0953-2048/23/5/054009
Lu, Xin, Park, W. K., Yuan, H. Q., Chen, G. F,, Luo, G. L., Wang, N. L., Sefat, A. S., McGuire, Michael A, Jin, R., Sales, Brian C, Mandrus, David, Gillett, J, Sebastian, Suchitra, and Greene, L. H. 2010. "Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals". United States. https://doi.org/10.1088/0953-2048/23/5/054009.
@article{osti_988734,
title = {Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals},
author = {Lu, Xin and Park, W. K. and Yuan, H. Q. and Chen, G. F, and Luo, G. L. and Wang, N. L. and Sefat, A. S. and McGuire, Michael A and Jin, R. and Sales, Brian C and Mandrus, David and Gillett, J and Sebastian, Suchitra and Greene, L. H.},
abstractNote = {Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe{sub 2}As{sub 2} (A = Ba, Sr) family (Fe-122). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} and Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, and the other with a V{sup 2/3} background conductance universally observed, extending even up to 100 meV for Sr{sub 0.6}Na{sub 0.4}Fe{sub 2}As{sub 2} and Sr(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}. The latter is also observed in point-contact junctions on the nonsuperconducting parent compound BaFe{sub 2}As{sub 2} and superconducting (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder-Tinkham-Klapwijk model, the data show a gap size of {approx} 3.0-4.0 meV with 2{Delta}{sub 0}/k{sub B}T{sub c} {approx} 2.0-2.6, consistent with the smaller gap size reported for the LnFeAsO family (Fe-1111). For the Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, the G(V) curves typically display a zero-bias conductance peak.},
doi = {10.1088/0953-2048/23/5/054009},
url = {https://www.osti.gov/biblio/988734}, journal = {Superconductor Science & Technology},
issn = {0953-2048},
number = 5,
volume = 23,
place = {United States},
year = {Fri Jan 01 00:00:00 EST 2010},
month = {Fri Jan 01 00:00:00 EST 2010}
}