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Entangled quantum state of magnetic dipoles

Ghosh, S. and Rosenbaum, T. F. and Aeppli, G. and Coppersmith, S. N. (2003) Entangled quantum state of magnetic dipoles. Nature, 425 (6953). pp. 48-51. ISSN 0028-0836. doi:10.1038/nature01888.

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Free magnetic moments usually manifest themselves in Curie laws, where weak external magnetic fields produce magnetizations that vary as the reciprocal of the temperature (1/T). For a variety of materials that do not display static magnetism, including doped semiconductors and certain rare-earth intermetallics, the 1/T law is replaced by a power law T^-α with α < 1. Here we show that a much simpler material system—namely, the insulating magnetic salt LiHo_xY_(1-x)F_4—can also display such a power law. Moreover, by comparing the results of numerical simulations of this system with susceptibility and specific-heat data, we show that both energy-level splitting and quantum entanglement are crucial to describing its behaviour. The second of these quantum mechanical effects—entanglement, where the wavefunction of a system with several degrees of freedom cannot be written as a product of wavefunctions for each degree of freedom—becomes visible for remarkably small tunnelling terms, and is activated well before tunnelling has visible effects on the spectrum. This finding is significant because it shows that entanglement, rather than energy-level redistribution, can underlie the magnetic behaviour of a simple insulating quantum spin system.

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Additional Information:© 2003 Nature Publishing Group. Received 29 April; accepted 7 July 2003. We thank R. Parthasarathy for discussions. The work at the University of Chicago was supported by the MRSEC Program of the National Science Foundation, that in the University of Wisconsin by the Petroleum Research Fund and the National Science Foundation, and that in University College London by a Wolfson–Royal Society Research Merit Award and the Basic Technologies programme of the UK Research Councils. The authors declare that they have no competing financial interests.
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Petroleum Research FundUNSPECIFIED
Wolfson Royal Society Research Merit AwardUNSPECIFIED
Research Councils UK (RCUK)UNSPECIFIED
Issue or Number:6953
Record Number:CaltechAUTHORS:20140707-163029073
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46957
Deposited By: George Porter
Deposited On:14 Jul 2014 16:49
Last Modified:10 Nov 2021 17:32

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