The role of water in wet cobaltate superconductor
Abstract
Superconductivity was recently observed for Na_xCoO_2-yH_2O near the composition x=0.35 and y=1.3. It has attracted much attention because of the similarity to the superconductivity in the cuprates. A key question to be answered before understanding the mechanism of superconductivity is the role of water. Initially it was assumed that its principal role was to separate the CoO2 layers, enhance the two-dimensionality and increase spin fluctuations. We report the results of our neutron diffraction and EELS measurements that suggest a more positive role of water. The pulsed neutron data with deutrated samples were analyzed by the atomic pair-density function (PDF) method. The diffraction spectrum has an unusually strong background, which is suspected to originate from incoherent motion of deuterium. The PDF shows that water molecules are strongly modified in this compound. Oxygen has only one D neighbor and D-D correlation is very weak. A possible model to explain the observations is dynamic hydrogen bond, which makes dynamic deuterium invisible to the PDF. We discuss the possibility of water participating in electron conduction and superconductivity.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARJ16007E