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Title: Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions

Abstract

In the quest to understand high-temperature superconductivity in copper oxides, debate has been focused on the pseudogap—a partial energy gap that opens over portions of the Fermi surface in the ‘normal’ state above the bulk critical temperature. The pseudogap has been attributed to precursor superconductivity, to the existence of preformed pairs and to competing orders such as charge-density waves. A direct determination of the charge of carriers as a function of temperature and bias could help resolve among these alternatives. Here we report measurements of the shot noise of tunnelling current in high-quality La 2-xSr xCuO 4/La 2CuO 4/La 2-xSr xCuO 4 (LSCO/LCO/LSCO) heterostructures fabricated using atomic layer-by-layer molecular beam epitaxy at several doping levels. The data delineate three distinct regions in the bias voltage–temperature space. Well outside the superconducting gap region, the shot noise agrees quantitatively with independent tunnelling of individual charge carriers. Deep within the superconducting gap, shot noise is greatly enhanced, reminiscent of multiple Andreev reflections. Above the critical temperature and extending to biases much larger than the superconducting gap, there is a broad region in which the noise substantially exceeds theoretical expectations for single-charge tunnelling, indicating pairing of charge carriers. These pairs are detectable deep intomore » the pseudogap region of temperature and bias. The presence of these pairs constrains current models of the pseudogap and broken symmetry states, while phase fluctuations limit the domain of superconductivity.« less

Authors:
 [1];  [1];  [2];  [3];  [4];  [4];  [4];  [5]; ORCiD logo [6];  [1]
  1. Rice Univ., Houston, TX (United States)
  2. Peking Univ., Beijing (China)
  3. Univ. of Connecticut, Storrs, CT (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
  5. Yale Univ., New Haven, CT (United States)
  6. Brookhaven National Lab. (BNL), Upton, NY (United States); Yale Univ., New Haven, CT (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1566821
Report Number(s):
BNL-212109-2019-JAAM
Journal ID: ISSN 0028-0836
Grant/Contract Number:  
SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal Volume: 572; Journal Issue: 7770; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Zhou, Panpan, Chen, Liyang, Liu, Yue, Sochnikov, Ilya, Bollinger, Anthony T., Han, Myung-Geun, Zhu, Yimei, He, Xi, Boz̆ović, Ivan, and Natelson, Douglas. Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions. United States: N. p., 2019. Web. doi:10.1038/s41586-019-1486-7.
Zhou, Panpan, Chen, Liyang, Liu, Yue, Sochnikov, Ilya, Bollinger, Anthony T., Han, Myung-Geun, Zhu, Yimei, He, Xi, Boz̆ović, Ivan, & Natelson, Douglas. Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions. United States. doi:10.1038/s41586-019-1486-7.
Zhou, Panpan, Chen, Liyang, Liu, Yue, Sochnikov, Ilya, Bollinger, Anthony T., Han, Myung-Geun, Zhu, Yimei, He, Xi, Boz̆ović, Ivan, and Natelson, Douglas. Wed . "Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions". United States. doi:10.1038/s41586-019-1486-7.
@article{osti_1566821,
title = {Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions},
author = {Zhou, Panpan and Chen, Liyang and Liu, Yue and Sochnikov, Ilya and Bollinger, Anthony T. and Han, Myung-Geun and Zhu, Yimei and He, Xi and Boz̆ović, Ivan and Natelson, Douglas},
abstractNote = {In the quest to understand high-temperature superconductivity in copper oxides, debate has been focused on the pseudogap—a partial energy gap that opens over portions of the Fermi surface in the ‘normal’ state above the bulk critical temperature. The pseudogap has been attributed to precursor superconductivity, to the existence of preformed pairs and to competing orders such as charge-density waves. A direct determination of the charge of carriers as a function of temperature and bias could help resolve among these alternatives. Here we report measurements of the shot noise of tunnelling current in high-quality La2-xSrxCuO4/La2CuO4/La2-xSrxCuO4 (LSCO/LCO/LSCO) heterostructures fabricated using atomic layer-by-layer molecular beam epitaxy at several doping levels. The data delineate three distinct regions in the bias voltage–temperature space. Well outside the superconducting gap region, the shot noise agrees quantitatively with independent tunnelling of individual charge carriers. Deep within the superconducting gap, shot noise is greatly enhanced, reminiscent of multiple Andreev reflections. Above the critical temperature and extending to biases much larger than the superconducting gap, there is a broad region in which the noise substantially exceeds theoretical expectations for single-charge tunnelling, indicating pairing of charge carriers. These pairs are detectable deep into the pseudogap region of temperature and bias. The presence of these pairs constrains current models of the pseudogap and broken symmetry states, while phase fluctuations limit the domain of superconductivity.},
doi = {10.1038/s41586-019-1486-7},
journal = {Nature (London)},
number = 7770,
volume = 572,
place = {United States},
year = {2019},
month = {8}
}

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Works referenced in this record:

High-temperature interface superconductivity between metallic and insulating copper oxides
journal, October 2008

  • Gozar, A.; Logvenov, G.; Kourkoutis, L. Fitting
  • Nature, Vol. 455, Issue 7214, p. 782-785
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