A notable aspect of high-temperature superconductivity in the copper oxides is the unconventional nature of the underlying paired-electron state. A direct manifestation of the unconventional state is a pairing energy—that is, the energy required to remove one electron from the superconductor—that varies (between zero and a maximum value) as a function of momentum, or wavevector1,2: the pairing energy for conventional superconductors is wavevector-independent3,4. The wavefunction describing the superconducting state will include the pairing not only of charges, but also of the spins of the paired charges. Each pair is usually in the form of a spin singlet5, so there will also be a pairing energy associated with transforming the spin singlet into the higher-energy spin triplet form without necessarily unbinding the charges. Here we use inelastic neutron scattering to determine thewavevector-dependence of spin pairing in La2−xSrxCuO4, the simplest high-temperature superconductor. We find that the spin pairing energy (or ‘spin gap’) is wavevector independent, even though superconductivity significantly alters the wavevector dependence of the spin fluctuations at higher energies.
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Shen, Z.-X. et al . Anomalously large gap anisotropy in the a–b plane of Bi2Sr2CaCu2O8+y . Phys. Rev. Lett. 70, 1553–1556 (1993).
Ding, H. et al . Angle-resolved photoemission spectroscopy study of the superconducting gap anisotropy in Bi2Sr2CaCu2O8+y . Phys. Rev. B 54, R9678–R9681 (1996).
Miyake, K., Schmitt-Rink, S. & Varma, C. M. Spin-fluctuation-mediated even-parity pairing in heavy-fermion superconductors. Phys. Rev. B 34, 6554–6556 (1986).
Scalapino, D. J., Loh, E. J & Hirsch, J. E. d-wave pairing near a spin-density-wave instability. Phys. Rev. B 34, 8190–8195 (1986).
Bardeen, J., Cooper, L. N. & Schrieffer, J. R. Theory of superconductivity. Phys. Rev. 61, 1175–1185 (1957).
Vaknin, D. et al . Antiferromagnetism in La2CuO4. Phys. Rev. Lett. 58, 2802–2805 (1987).
Mook, H. A. et al . Spin fluctuations in YBa2Cu3O6.6. Nature 395, 580–582 (1998).
Cheong, S.-W. Incommensurate magnetic fluctuations in La2−x Sr x CuO4. Phys. Rev. Lett.; 67, 1791–1794 (1991).
Mason, T. E., Aeppli, G. & Mook, H. A. Magnetic dynamics of superconducting La1.86Sr0.14CuO4. Phys. Rev. Lett. 68, 1414–1417 (1992).
Mason, T. E., Schröder, A., Aeppli, G., Mook, H. A. & Hayden, S. M. New magnetic coherence effect in superconducting La2−x Sr x CuO4. Phys. Rev. Lett. 77, 1604–1607 (1996).
Yamada, K. et al . Direct observation of a magnetic gap in superconducting La1.85Sr0.15CuO4(T c= 37.3 K). Phys. Rev. Lett. 75, 1626–1629 (1995).
Petit, S., Moudden, A. H., Hennion, B., Vietkin, A. & Revcolevschi, A. Spin dynamics study of La2−x Sr x CuO4by inelastic neutron scattering. Physica B 234–236, 800–802 (1997).
Mason, T. E., Aeppli, G., Hayden, S. M., Ramirez, A. P. & Mook, H. A. Magnetic fluctuations in superconducting La2−x Sr x CuO4. Physica B 199–200, 284–287 (1994).
Mason, T. E., Aeppli, G., Hayden, S. M., Ramirez, A. P. & Mook, H. A. Low energy excitations in superconducting La1.86Sr0.14CuO4. Phys. Rev. Lett. 71, 919–921 (1993).
Joynt, R. & Rice, T. M. Magnetic properties of anisotropic superconductors. Phys. Rev. B 38, 2345–2353 (1988).
Tanamato, T., Kohno, H. & Fukuyama, H. Magnetic properties of extended t-J model. II. Dynamical properties. J. Phys. Soc. Jpn 63, 2739–2759 (1994).
Rendell, J. M. & Carbotte, J. P. Effects of gap and band anisotropy on spin susceptibility in the oxide superconductors. Phys. Rev. B 53, 589–5899 (1996).
Zha, Y., Levin, K. & Si, Q. Neutron experiments as a test of anisotropic pairing in YBa2Cu3O7−y and La2−x Sr x CuO4. Phys. Rev. B 47, 9124–9127 (1993).
Bulut, N. & Scalapino, D. J. Neutron scattering in a d x 2 - x 1 -wave superconductor. Phys. Rev. B 50, 16078–16081 (1993).
Morr, D. K. & Pines, D. The effect of superconductivity on the incommensurate magnetic response of cuprate superconductors. Preprint cond-mat/9807214 at 〈http://xxx.lanl.gov〉 (1998).
Tsuei, C. C. et al . Pairing symmetry in single-layer tetragonal Tl2Ba2CuO6+δsuperconductors. Science 271, 329–322 (1996).
Chen, X. K., Irwin, J. C., Trodahl, H. J., Kimura, T. & Kishio, K. Investigation of the superconducting gap La2−x Sr x CuO4by Raman spectroscopy. Phys. Rev. Lett. 73, 3290–3292 (1994).
Luther, A. & Emery, V. J. Backward scattering in the one-dimensional electron gas. Phys. Rev. Lett. 33, 589–592 (1974).
Rokhsar, D. S. & Kivelson, S. A. Superconductivity and the quantum hard-core dimer gas. Phys. Rev. Lett. 61, 2376–2379 (1988).
Tsunetsugu, H. Doped spin-liquid antiferromagnets and Luther-Emery liquid. Physica B 237–238, 108–111 (1997).
Dagotto, E., Riera, J. & Scalapino, D. Superconductivity in ladders and coupled planes. Phys. Rev. B 45, 5744–5747 (1992).
Rice, T. M., Gopalan, S. & Sigrist, M. Superconductivity, spin gaps and Luttinger liquids in a class of cuprates. Europhys. Lett. 23, 445–449 (1993).
Emery, V. J., Kivelson, S. A. & Zachar, O. Spin-gap proximity effect mechanism of high-temperature superconductivity. Phys. Rev. B 56, 6120–6147 (1997).
Andoh, Y. et al . Resistive upper critical fields and irreversibility lines of optimally doped high-T ccuprates. Preprint (Bell Laboratories, Murray Hill, NJ 07974, USA, (1998).
Mason, T. E., Clausen, K. N., Aeppli, G., McMorrow, D. F. & Kjems, J. K. RITA: The reinvented triple-axis spectrometer. Can. J. Phys. 73, 697–702 (1995).
We thank K. N. Clausen for help and support during the experiments, and B.Batlogg, G. Boebinger, V. Emery, S. Kivelson, H. Mook, D. Morr, D. Pines, Z.-X. Shen, C.-C. Tsuei and J. Zaanen for discussions. Work done at the University of Toronto was sponsored by the Natural Sciences and Engineering Research Council and the Canadian Institute for Advanced Research, while work done at Oak Ridge was supported by the US DOE. T.E.M. was supported by the Alfred P. Sloan Foundation, and A.S. was supported by the TMR program.
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Lake, B., Aeppli, G., Mason, T. et al. Spin gap and magnetic coherence in a clean high-temperature superconductor. Nature 400, 43–46 (1999). https://doi.org/10.1038/21840
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