Hidden magnetic excitation in the pseudogap phase of a high-Tc superconductor
Yuan Li1,10, V. Balédent2, G. Yu3, N. Barišić4,5,10, K. Hradil6, R. A. Mole7, Y. Sidis2, P. Steffens8, X. Zhao4,9, P. Bourges2 & M. Greven3
- Department of Physics, Stanford University, Stanford, California 94305, USA
- Laboratoire Léon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif sur Yvette, France
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
- T.H. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
- Institut für Physikalische Chemie, Universität Göttingen, 37077 Göttingen, Germany
- Forschungsneutronenquelle Heinz Maier-Leibnitz, 85747 Garching, Germany
- Institut Laue Langevin, 38042 Grenoble Cedex 9, France
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, China
- Present addresses: Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany (Y.L.); Institute of Physics, Bijenicka cesta 46, 10 000 Zagreb, Croatia (N.B.).
Correspondence to: M. Greven3 Email: greven@physics.umn.edu
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Abstract
The elucidation of the pseudogap phenomenon of the high-transition-temperature (high-Tc) copper oxides—a set of anomalous physical properties below the characteristic temperature T* and above Tc—has been a major challenge in condensed matter physics for the past two decades1. Following initial indications of broken time-reversal symmetry in photoemission experiments2, recent polarized neutron diffraction work demonstrated the universal existence of an unusual magnetic order below T* (refs 3, 4). These findings have the profound implication that the pseudogap regime constitutes a genuine new phase of matter rather than a mere crossover phenomenon. They are furthermore consistent with a particular type of order involving circulating orbital currents, and with the notion that the phase diagram is controlled by a quantum critical point5. Here we report inelastic neutron scattering results for HgBa2CuO4+δ that reveal a fundamental collective magnetic mode associated with the unusual order, and which further support this picture. The mode’s intensity rises below the same temperature T* and its dispersion is weak, as expected for an Ising-like order parameter6. Its energy of 52–56 meV renders it a new candidate for the hitherto unexplained ubiquitous electron–boson coupling features observed in spectroscopic studies7, 8, 9, 10.
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