1. Enhanced high-pressure superconductivity and local structure of theBa8Si46clathrate
- Author
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S. Le Floch, Jean-Paul Itié, Pierre Lagarde, Pierre Toulemonde, Anne-Marie Flank, Manuel Núñez-Regueiro, Alfonso San-Miguel, Vittoria Pischedda, Denis Machon, and F. Morales
- Subjects
Coupling constant ,Superconductivity ,Materials science ,Condensed matter physics ,Absorption spectroscopy ,Clathrate hydrate ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Local structure ,Condensed Matter::Materials Science ,Electrical resistance and conductance ,Volume (thermodynamics) ,Condensed Matter::Superconductivity ,Phase (matter) ,0103 physical sciences ,010306 general physics ,0210 nano-technology - Abstract
The high-pressure superconducting properties and the local structure of the Ba8Si46 clathrate have been studied using electrical resistance and x-ray absorption spectroscopy measurements up to more than 20 GPa. At pressures above 10–13 GPa, corresponding to a well-known volume collapse phase transformation, a sudden increase in the critical temperature leads to a maximum value of the superconducting critical temperature Tc of ∼8.5–9 K at 20 GPa. In the low-pressure clathrate phase, the superconducting critical temperature decreases as pressure is applied with an electron-phonon coupling constant λ=1.1 derived from the temperature evolution of the electrical resistance at different pressures. A progressive disorder in the Ba-Si correlations in the Ba@Si24 cages of the structure is observed for pressures beyond ∼5 GPa. These observations exclude a structural homothecy at the volume collapse transition. The high-pressure collapsed phase of Ba8Si46 is then associated with local structural changes and shows enhanced superconducting properties.
- Published
- 2016