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Title: Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors

Abstract

The surface terminations of 122-type alkaline earth metal iron pnictides AEFe2As2(AE=Ca,Ba) are investigated with scanning tunneling microscopy/spectroscopy. Cleaving these crystals at a cryogenic temperature yields a large majority of terminations with an atomically resolved (√2 × √2)R45 or 1 × 2 lattice, as well as a very rare termination of 1 × 1 lattice symmetry. By assessing the lattice registration and selective chemical marking, we identify these terminations as (√2 × √2)R45-reconstructed AE, 1 × 2-reconstructed As, and (√2 × √2)R45-reconstructed Fe surface layers, respectively. Layer-resolved tunneling spectroscopy on these terminating surfaces reveals a well-defined superconducting energy gap on the As terminations, while the gap features become weaker on the AE terminations and absent on the Fe terminations. The superconducting gap is hardly affected locally by the As or AE surface reconstructions. The definitive identification of the surface terminations and the associated spectroscopic signatures shed light on the necessary roles of As and the pnictogen-iron-pnictogen trilayer building block in iron-based superconductivity.

Authors:
 [1];  [2];  [3];  [3];  [4]; ORCiD logo [5]; ORCiD logo [5];  [5]; ORCiD logo [5];  [6];  [7];  [7];  [8];  [3];  [2];  [3];  [3];  [9]
+ Show Author Affiliations
  1. Univ. of Houston, TX (United States). Dept. of Physics and Texas Center for Superconductivity; Chinese Academy of Sciences (CAS), Shanghai (China). Shanghai Inst. of Microsystem and Information Technology
  2. Chinese Academy of Sciences (CAS), Beijing (China). Beijing National Lab. for Condensed Matter Physics and Inst. of Physics
  3. Univ. of Houston, TX (United States). Dept. of Physics and Texas Center for Superconductivity
  4. Univ. of Houston, TX (United States). Dept. of Physics and Texas Center for Superconductivity; Boston College, Chestnut Hill, MA (United States). Dept. of Physics
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  6. Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Physics & Astronomy
  7. Rice Univ., Houston, TX (United States). Dept. of Physics and Astronomy
  8. Univ. of Houston, TX (United States). Dept. of Physics and Texas Center for Superconductivity; Univ. of Texas at Dallas, Richardson, TX (United States). Dept. of Physics
  9. Univ. of Houston, TX (United States). Dept. of Physics and Texas Center for Superconductivity; Chinese Academy of Sciences (CAS), Beijing (China). Beijing National Lab. for Condensed Matter Physics and Inst. of Physics; Chinese Academy of Sciences (CAS), Beijing (China). School of Physics; Chinese Academy of Sciences (CAS), Beijing (China). CAS Center for Excellence in Topological Quantum Computation; Songshang Lake Material Lab., Dongguan (China)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1561639
Alternate Identifier(s):
OSTI ID: 1509926
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 99; Journal Issue: 13; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Li, Ang, Yin, Jia-Xin, Wang, Jihui, Wu, Zheng, Ma, Jihua, Sefat, Athena Safa, Sales, Brian C., Mandrus, David, McGuire, Michael A., Jin, Rongying, Zhang, Chenglin, Dai, Pengcheng, Lv, Bing, Chu, Ching-Wu, Liang, Xuejin, Hor, P, Ting, C, and Pan, Shuheng. Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors. United States: N. p., 2019. Web. doi:10.1103/physrevb.99.134520.
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Li, Ang, Yin, Jia-Xin, Wang, Jihui, Wu, Zheng, Ma, Jihua, Sefat, Athena Safa, Sales, Brian C., Mandrus, David, McGuire, Michael A., Jin, Rongying, Zhang, Chenglin, Dai, Pengcheng, Lv, Bing, Chu, Ching-Wu, Liang, Xuejin, Hor, P, Ting, C, & Pan, Shuheng. Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors. United States. https://doi.org/10.1103/physrevb.99.134520
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Li, Ang, Yin, Jia-Xin, Wang, Jihui, Wu, Zheng, Ma, Jihua, Sefat, Athena Safa, Sales, Brian C., Mandrus, David, McGuire, Michael A., Jin, Rongying, Zhang, Chenglin, Dai, Pengcheng, Lv, Bing, Chu, Ching-Wu, Liang, Xuejin, Hor, P, Ting, C, and Pan, Shuheng. Tue . "Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors". United States. https://doi.org/10.1103/physrevb.99.134520. https://www.osti.gov/servlets/purl/1561639.
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@article{osti_1561639,
title = {Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors},
author = {Li, Ang and Yin, Jia-Xin and Wang, Jihui and Wu, Zheng and Ma, Jihua and Sefat, Athena Safa and Sales, Brian C. and Mandrus, David and McGuire, Michael A. and Jin, Rongying and Zhang, Chenglin and Dai, Pengcheng and Lv, Bing and Chu, Ching-Wu and Liang, Xuejin and Hor, P and Ting, C and Pan, Shuheng},
abstractNote = {The surface terminations of 122-type alkaline earth metal iron pnictides AEFe2As2(AE=Ca,Ba) are investigated with scanning tunneling microscopy/spectroscopy. Cleaving these crystals at a cryogenic temperature yields a large majority of terminations with an atomically resolved (√2 × √2)R45 or 1 × 2 lattice, as well as a very rare termination of 1 × 1 lattice symmetry. By assessing the lattice registration and selective chemical marking, we identify these terminations as (√2 × √2)R45-reconstructed AE, 1 × 2-reconstructed As, and (√2 × √2)R45-reconstructed Fe surface layers, respectively. Layer-resolved tunneling spectroscopy on these terminating surfaces reveals a well-defined superconducting energy gap on the As terminations, while the gap features become weaker on the AE terminations and absent on the Fe terminations. The superconducting gap is hardly affected locally by the As or AE surface reconstructions. The definitive identification of the surface terminations and the associated spectroscopic signatures shed light on the necessary roles of As and the pnictogen-iron-pnictogen trilayer building block in iron-based superconductivity.},
doi = {10.1103/physrevb.99.134520},
journal = {Physical Review B},
number = 13,
volume = 99,
place = {United States},
year = {Tue Apr 30 00:00:00 EDT 2019},
month = {Tue Apr 30 00:00:00 EDT 2019}
}
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https://doi.org/10.1103/physrevb.99.134520
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