Spiral magnetic order and pressure-induced superconductivity in transition metal compounds
Magnetic and superconducting ground states can compete, cooperate and coexist. MnP provides a compelling and potentially generalizable example of a material where superconductivity and magnetism may be intertwined. Using a synchrotron-based non-resonant X-ray magnetic diffraction technique, we reveal a spiral spin order in MnP and trace its pressure evolution towards superconducting order via measurements in a diamond anvil cell. Judging from the magnetostriction, ordered moments vanish at the quantum phase transition as pressure increases the electron kinetic energy. Spins remain local in the disordered phase, and the promotion of superconductivity is likely to emerge from an enhanced coupling to residual spiral spin fluctuations and their concomitant suppression of phonon-mediated superconductivity. As the pitch of the spiral order varies across the 3d transition metal compounds in the MnP family, the magnetic ground state switches between antiferromagnet and ferromagnet, providing an additional tuning parameter in probing spin-fluctuation-induced superconductivity.
Additional Information© 2016 Macmillan Publishers Limited. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ Received: 14 March 2016. Accepted: 29 August 2016. Published online: 06 October 2016. We thank P.B. Littlewood for helpful conversations. We are grateful to B. Fisher for assisting with the magnetization measurements. Sample preparation at the MRSEC facilities of the University of Chicago was supported by NSF Grant No. DMR-1420709. The work at the California Institute of Technology was supported by U.S. Department of Energy Basic Energy Sciences Award DE-SC0014866. The use of the Advanced Photon Source and the Center for Nanoscale Materials of Argonne National Laboratory was supported by the U.S. Department of Energy Office of Science User Facilities under contract No. DE-AC02-06CH11357. J.-G.C. and J.L.L. were supported by the MOST and NSF of China, and the Strategic Priority Research Program of the Chinese Academy of Sciences. Author Contributions: Y.F. and T.F.R. designed the research. J.-G.C., W.W. and J.L.L. provided samples. Y.W. and Y.F. performed measurements and developed the theoretical framework. Y.W., Y.F. and T.F.R. prepared the manuscript. All authors commented. Data availability: The data that support the findings of this study are available from the corresponding authors upon request. The authors declare no competing financial interests.
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