engleski

Suppression of the Charge-Density Wave State in Sr14Cu24O41 by Calcium Doping

The charge response in the spin chain and ladder compound Sr14-xCaxCu24O41 is characterized by dc resistivity, low-frequency dielectric spectroscopy and optical spectroscopy. We identify an insulator-to-insulator phase transition below which a charge-density wave (CDW) develops in the ladder arrays. Calcium doping suppresses this phase with the transition temperature decreasing from 210 K for x=0 down to 7 K for x=9, and the CDW gap from 130 meV down to 3 meV, respectively. Whereas at high doping levels the competing CDW order fully vanishes, external pressure is needed to suppress an insulating high-temperature phase and to establish superconductivity. We propose that this is due to increased disorder and two-dimensionality induced by a subtle interplay of both doping and pressure.

spin ladders; charge-density wave; low-frequency dielectric spectroscopy; optical spectroscopy

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