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Phys. Rev. Lett. 98, 027403 (2007) [4 pages]

One- and Two-Triplon Spectra of a Cuprate Ladder

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S. Notbohm1,2, P. Ribeiro3, B. Lake1,4, D. A. Tennant1,4, K. P. Schmidt5, G. S. Uhrig6, C. Hess3, R. Klingeler3, G. Behr3, B. Büchner3, M. Reehuis1,9, R. I. Bewley7, C. D. Frost7, P. Manuel7, and R. S. Eccleston8
1Hahn-Meitner-Institut Berlin, Glienicker Straße 100, 14109 Berlin, Germany
2School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom
3Leibniz-Institut for Solid State and Material Research, IFW-Dresden, 01171 Dresden, Germany
4Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
5Institute of Theorectical Physics, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
6Lehrstuhl für Theoretische Physik I, Universität Dortmund, 44221 Dortmund, Germany
9Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany
7ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 OQX, United Kingdom
8Materials and Engineering Research Institute, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, United Kingdom

Received 13 March 2006; published 12 January 2007

We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41 as a starting point for investigating doped ladders and their tendency toward superconductivity. A key feature was the separation of one-triplon and two-triplon scattering. Two-triplon scattering is observed quantitatively for the first time and so access is realized to the important strong magnetic quantum fluctuations. The spin gap is found to be 26.4±0.3  meV. The data are successfully modeled using the continuous unitary transformation method, and the exchange constants are determined by fitting to be Jleg=186  meV and Jrung=124  meV along the leg and rung, respectively; a substantial cyclic exchange of Jcyc=31  meV is confirmed.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.98.027403
DOI:
10.1103/PhysRevLett.98.027403
PACS:
78.70.Nx, 75.10.Jm, 75.30.Ds, 75.30.Et
 
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