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Phys. Rev. Lett. 106, 117401 (2011) [4 pages]

Singlet-Triplet Excitations in the Unconventional Spin-Peierls TiOBr Compound

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J. P. Clancy1, B. D. Gaulin1,2,3, C. P. Adams4, G. E. Granroth5, A. I. Kolesnikov5, T. E. Sherline5, and F. C. Chou6
1Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada
2Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, L8S 4M1, Canada
3Canadian Institute for Advanced Research, 180 Dundas Street West, Toronto, Ontario, M5G 1Z8, Canada
4Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W5, Canada
5Neutron Scattering Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
6Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan

Received 21 September 2010; published 18 March 2011

We have performed time-of-flight neutron scattering measurements on powder samples of the unconventional spin-Peierls compound TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the Spallation Neutron Source at Oak Ridge National Laboratory. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate spin-Peierls phases, which we associate with n=1 and n=2 triplet excitations out of the singlet ground state. These results represent the first direct measurement of the singlet-triplet energy gap in TiOBr, which has a value of Eg=21.2±1.0  meV.

© 2011 American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.106.117401
DOI:
10.1103/PhysRevLett.106.117401
PACS:
78.70.Nx, 75.10.Pq, 75.40.Gb, 75.50.Ee
 
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