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Spin susceptibility of charge-ordered YBa2Cu3Oy across the upper critical field

  1. Marc-Henri Juliena,3
  1. aLaboratoire National des Champs Magnétiques Intenses, CNRS–Université Grenoble Alpes–Université Paul Sabatier–Institut National des Sciences Appliquées–European Magnetic Field Laboratory, 38042 Grenoble, France;
  2. bNational High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310;
  3. cDepartment of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada;
  4. dCanadian Institute for Advanced Research, Toronto, ON M5G 1Z8, Canada
  1. Edited by Zachary Fisk, University of California, Irvine, CA, and approved October 27, 2017 (received for review June 26, 2017)


The upper critical field <mml:math><mml:msub><mml:mi>H</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>Hc2 is a fundamental, and technologically important, property that measures the ability of a superconductor to withstand magnetic fields. Recently, there has been a controversy regarding the values Hc2 in high-Tc copper oxides, particularly in YBa2Cu3Oy when a charge density wave (CDW) is present. Here, taking advantage of nuclear magnetic resonance, a local probe that can measure the intrinsic spin susceptibility <mml:math><mml:msub><mml:mi>χ</mml:mi><mml:mi>spin</mml:mi></mml:msub></mml:math>χspin of the superconducting planes, we observe an essentially linear increase in <mml:math><mml:msub><mml:mi>χ</mml:mi><mml:mi>spin</mml:mi></mml:msub></mml:math>χspin up to a point in the range of 20–40 T, followed by a constant value. This saturation point is in accord with previous measurements of Hc2. Our data suggest that the CDW drastically reduces <mml:math><mml:msub><mml:mi>H</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>Hc2 in YBa2Cu3Oy.


The value of the upper critical field Hc2, a fundamental characteristic of the superconducting state, has been subject to strong controversy in high-Tc copper oxides. Since the issue has been tackled almost exclusively by macroscopic techniques so far, there is a clear need for local-probe measurements. Here, we use 17O NMR to measure the spin susceptibility <mml:math><mml:msub><mml:mi>χ</mml:mi><mml:mi>spin</mml:mi></mml:msub></mml:math>χspin of the CuO2 planes at low temperature in charge-ordered YBa2Cu3Oy. We find that <mml:math><mml:msub><mml:mi>χ</mml:mi><mml:mi>spin</mml:mi></mml:msub></mml:math>χspin increases (most likely linearly) with magnetic field H and saturates above field values ranging from 20 T to 40 T. This result is consistent with the lowest Hc2 values claimed previously and with the interpretation that the charge density wave (CDW) reduces Hc2 in underdoped YBa2Cu3Oy. Furthermore, the absence of marked deviation in <mml:math><mml:mrow><mml:msub><mml:mi>χ</mml:mi><mml:mi>spin</mml:mi></mml:msub><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mi>H</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:mrow></mml:math>χspin(H) at the onset of long-range CDW order indicates that this <mml:math><mml:msub><mml:mi>H</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>Hc2 reduction and the Fermi-surface reconstruction are primarily rooted in the short-range CDW order already present in zero field, not in the field-induced long-range CDW order. Above <mml:math><mml:msub><mml:mi>H</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>Hc2, the relatively low values of <mml:math><mml:msub><mml:mi>χ</mml:mi><mml:mi>spin</mml:mi></mml:msub></mml:math>χspin at <mml:math><mml:mrow><mml:mpadded width="+1.7pt"><mml:mi>T</mml:mi></mml:mpadded><mml:mo>=</mml:mo><mml:mn>?2</mml:mn></mml:mrow></mml:math>T=?2 K show that the pseudogap is a ground-state property, independent of the superconducting gap.


  • ?1Present address: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.

  • ?2Present address: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Anhui, Hefei 230026, People’s Republic of China.

  • ?3To whom correspondence should be addressed. Email: marc-henri.julien{at}lncmi.cnrs.fr.
  • Author contributions: R.Z., M.H., T.W., I.V., H.M., S.K., A.P.R., P.L.K., R.L., W.N.H., D.A.B., and M.-H.J. performed research; R.Z., M.H., T.W., I.V., H.M., and M.-H.J. analyzed data; and M.-H.J. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1711445114/-/DCSupplemental.

Published under the PNAS license.

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