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TT: Fachverband Tiefe Temperaturen

TT 3: CE: Charge Density Wave \& Peierls Instability

TT 3.1: Talk

Monday, March 14, 2011, 10:30–10:45, HSZ 304

Infrared study of the blue bronze K_0.3MoO₃ — •Rebecca Beyer, Neven Barišić, and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, Germany

The blue bronzes A_0.3MoO₃ (A = Rb, K, Tl) are well known quasi-one-dimensional materials. They exhibit a Peierls-type metal-insulator phase transition around 180 K which is connected to the formation of a charge density wave (CDW) in the conducting direction. While temperature dependent dc-resistivity indicates the CDW in all three directions, so far most measurements concentrated on the conducting b- and a*-direction and no thorough investigations of the physical properties of the insulating c*-direction have been carried out.
We report first optical conductivity measurements on the potassium blue bronze K_0.3MoO₃ along the b- and the c*-direction in order to evaluate the influence of the long range order of the CDW on the perpendicular direction. Measurements were performed with polarized light in a wide frequency range from 30 cm⁻¹ up to 11000 cm⁻¹ for several selected temperatures between 300 K and 50 K. At high frequencies we have carefully analyzed the changes in the strong interband transition related to the gap opening. In addition two phonon lines are observed around 900 cm⁻¹ and attributed to stretching vibrations of terminal O- with Mo-atoms. Degenerated at high temperatures, those lines split and shift in frequency once the CDW develops.