Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Phasendiagramm der HTSL

TT 21.2: Hauptvortrag

Freitag, 28. März 2003, 10:40–11:10, HSZ304

Raman Scattering versus Infrared Conductivity: Evidence for 1D Conduction in La_2−xSr_xCuO₄ — •F. Venturini¹, Q.-M. Zhang², R. Hackl¹, A. Lucarelli³, S. Lupi³, M. Ortolani³, P. Calvani³, N. Kikugawa⁴, and T. Fujita⁴ — ¹Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany — ²National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093, P.R.China — ³INFM and Dipartimento di Fisica, Universita’ di Roma La Sapienza, Piazzale Aldo Moro 2, 00185 Roma, Italy — ⁴ADSM, Hiroshima University, Higashi-Hiroshima 739-8526, Japan

Raman and infrared (IR) spectra of under- and optimally doped LSCO have been measured as a function of symmetry and temperature. At high temperatures the Raman response is similar to that in other cuprates while the IR spectrum shows an anomalous absorption peak around 150-200 cm⁻¹. In the underdoped sample a new type of electronic state is observed in the Raman response below approximately 100 K characterized by a very long lifetime of electrons propagating along the Cu-O bonds. In the same sample the IR peak rapidly displaces to lower energies with decreasing temperatures. The first moments for both optical and Raman conductivity are calculated in the range between 20 and 200 cm⁻¹ and are found to have the same dependence on temperature indicating a common origin. These results are interpreted as a signature of an enhanced 1D dc transport within a charge-density-wave scenario.

[1] F. Venturini et al., Phys. Rev. B 66, 060502(R) (2002)