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Phys. Rev. Lett. 93, 147002 (2004) [4 pages]

Dispersive Excitations in the High-Temperature Superconductor La2-xSrxCuO4

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N. B. Christensen1, D. F. McMorrow1,2,3, H. M. Rønnow4,5, B. Lake6, S. M. Hayden7, G. Aeppli2, T. G. Perring3, M. Mangkorntong8, M. Nohara8, and H. Takagi9
1Materials Research Department, Risø National Laboratory, 4000 Roskilde, Denmark
2London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
3ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
4Laboratory for Neutron Scattering, ETH Zürich & PSI Villigen, CH-5232 Villigen PSI, Switzerland
5The James Franck Institute and Department of Physics, University of Chicago, Illinois 60637, USA
6Department of Physics, Oxford University, Oxford, OX1 3PU, United Kingdom
7H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
8Institute for Solid State Physics, University of Tokyo, Tokyo 113-8656, Japan
9Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8651, Japan

Received 17 March 2004; published 28 September 2004

High-resolution neutron scattering experiments on optimally doped La2-xSrxCuO4 (x=0.16) reveal that the magnetic excitations are dispersive. The dispersion is the same as in YBa2Cu3O6.85, and is quantitatively related to that observed with charge sensitive probes. The associated velocity in La2-xSrxCuO4 is only weakly dependent on doping with a value close to the spin-wave velocity of the insulating (x=0) parent compound. In contrast with the insulator, the excitations broaden rapidly with increasing energy, forming a continuum at higher energy and bear a remarkable resemblance to multiparticle excitations observed in 1D S=1/2 antiferromagnets. The magnetic correlations are 2D, and so rule out the simplest scenarios where the copper oxide planes are subdivided into weakly interacting 1D magnets.

© 2004 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.93.147002
DOI:
10.1103/PhysRevLett.93.147002
PACS:
74.72.Dn, 61.12.–q, 74.25.Ha
 
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