Europhys. Lett.
Volume 47, Number 6, September 1999
Page(s) 715 - 721
Section Condensed matter: electronic structure, electrical, magnetic and optical properties
Published online 01 September 2002
DOI: 10.1209/epl/i1999-00449-1

Europhys. Lett, 47 (6), pp. 715-721 (1999)

In-plane charge dynamics in ${\rm La}_{1.6-x}{\rm Nd}_{0.4}{\rm Sr}_{x}{\rm CuO}_4$: Absence of a charge gap in the spin/charge ordered state

S. Tajima 1 N. L. Wang 1, N. Ichikawa 2, H. Eisaki 2, S. Uchida 2, H. Kitano 3
T. Hanaguri 3 and A. Maeda 3

1 Superconductivity Research Laboratory, ISTEC - Tokyo 135-0062, Japan
2 Department of Applied Physics, The University of Tokyo - Tokyo 113-8656, Japan
3 Department of Basic Science, The University of Tokyo - Tokyo 153-0041, Japan

(received 10 June 1999; accepted 13 July 1999)

PACS. 74.25Gz - Optical properties.
PACS. 74.72Dn - La-based cuprates.
PACS. 71.27${\rm +a}$ - Strongly correlated electron systems; heavy fermions.


We have investigated the optical conductivity of the spin/charge "stripe'' order phase in ${\rm La}_{1.6-x}{\rm Nd}_{0.4}{\rm Sr}_{x}{\rm CuO}_4$in the microwave and the infrared regions. The in-plane conductivity is appreciably suppressed with respect to the spectrum for the Nd-free crystal over a wide frequency range of up to $\rm 8000\; cm^{-1}$. The suppression persists even at room temperature, indicating a strong fluctuation of this order. Nevertheless, the spectrum is basically metallic without showing a gap associated with charge order. It was found that the magnetic penetration depth is extremely long in the superconducting state which coexists with the static spin/charge order.


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