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Phys. Rev. Lett. 91, 087401 (2003) [4 pages]

Collective Density-Wave Excitations in Two-Leg Sr14-xCaxCu24O41 Ladders

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A. Gozar1,2, G. Blumberg1,*, P. B. Littlewood3, B. S. Dennis1, N. Motoyama4, H. Eisaki5, and S. Uchida4
1Lucent Technologies, Bell Laboratories, Murray Hill, New Jersey 07974, USA
2University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
3Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE United Kingdom
4The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan
5Stanford University, Stanford, California 94305, USA

Received 28 May 2002; published 19 August 2003

Raman measurements in the 1.5–20  cm-1 energy range were performed on single crystals of Sr14-xCaxCu24O41. A quasielastic scattering peak (QEP) which softens with cooling is observed only in the polarization parallel to the ladder direction for samples with x=0, 8, and 12. The QEP is a Raman fingerprint of pinned collective density wave excitations screened by uncondensed carriers in the ladder structures. Our results suggest that transport in metallic samples, which is similar to transport in underdoped high-Tc cuprates, is driven by a collective electronic response.

© 2003 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.91.087401
DOI:
10.1103/PhysRevLett.91.087401
PACS:
78.30.–j, 71.27.+a, 71.45.Lr

*To whom correspondence should be addressed.

Electronic address: girsh@bell-labs.com

 
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