Dresden 2003 – scientific programme

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TT: Tiefe Temperaturen

TT 9: Neue und unkonventionelle Supraleiter

TT 9.5: Talk

Tuesday, March 25, 2003, 10:30–10:45, HSZ301

SPIN-LADDER CUPRATE (La,Sr,Ca)₁₄Cu₂₄O₄₁ : FROM CDW TO SUPERCONDUCTIVITY — •Martin Dressel¹, B. Gorshunov¹, S. Tomic², T. Vuletic², B. Korin-Hamzic², and J. Akimitsu³ — ¹1.Physikalisches Institut, Universität stuttgart, Germany. — ²Instiotute of Physics, Zagreb, Croatia — ³Aoyama-Gakuin University, Tokyo, Japan

The charge response in the spin chain/ladder family (La,Sr,Ca)₁₄Cu₂₄O₄₁ is characterized by DC resistivity, dielectric and optical spectroscopy. We identify a phase transition to the charge-density wave (CDW) state in the ladders (conducting channel) in Sr₁₄Cu₂₄O₄₁. Calcium doping x, required to get superconductivity, suppresses the CDW with the transition temperature decreasing from 210 K for x=0 to 10 K for x=9, and the CDW gap from 130 meV to 3 meV, respectively. This suppression is due to the worse nesting, because the inter-ladder hopping integrals increase, and to disorder introduced at the Sr sites, altogether speaking in favor of two-dimensional superconductivity under pressure. We show that for the intermediate counts of charge carriers (holes) the charge-ordered gaped state in chains is suppressed in favor of a disorder-driven insulating state.