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Published January 1, 2011 | Published
Journal Article Open

Magnetism, structure, and charge correlation at a pressure-induced Mott-Hubbard insulator-metal transition

Abstract

We use synchrotron x-ray diffraction and electrical transport under pressure to probe both the magnetism and the structure of single-crystal NiS_2 across its Mott-Hubbard transition. In the insulator, the low-temperature antiferromagnetic order results from superexchange among correlated electrons and couples to a (1/2, 1/2, 1/2) superlattice distortion. Applying pressure suppresses the insulating state, but enhances the magnetism as the superexchange increases with decreasing lattice constant. By comparing our results under pressure to previous studies of doped crystals, we show that this dependence of the magnetism on the lattice constant is consistent for both band broadening and band filling. In the high-pressure metallic phase the lattice symmetry is reduced from cubic to monoclinic, pointing to the primary influence of charge correlations at the transition. There exists a wide regime of phase separation that may be a general characteristic of correlated quantum matter.

Additional Information

© 2011 American Physical Society. (Received 21 October 2010; published 11 January 2011) We are grateful to D. Robinson and J.-W. Kim for technical support at 6-ID-B of the Advanced Photon Source, and to X. Yao for growth of the crystals. The work at the University of Chicago was supported by NSF Grant No. DMR-0907025. Use of the Advanced Photon Source was supported by the U.S. Department of Energy Basic Energy Sciences under Contract No. NEAC02-06CH11357.

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Published - PhysRevB.83.035106.pdf

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