Anharmonicity in A15 Superconductors: A Thermal Expansion Approach
The highly anharmonic behaviour for the A15 compounds V3Si and Nb3Sn has been the subject of considerable theoretical and experimental study. The majority of theoretical treatments place the emphasis on the electronic contribution to the free energy.
Thermal expansion measurements provide a direct measure of an-harmonicity and measurements have been made for a number of A15 compounds. The expansion behaviour for V-Si and Nb-Sn compounds, close to the stoichiometric A3B composition, and V3Ge is found to be highly anomalous. In the case of the V-Si compounds, it is argued from an analysis of the expansion behaviour in the superconducting state that the lattice is responsible for the anharmonic properties. The anomalous expansion in the Nb-Sn compounds is intimately associated with the occurrence of the cubic-tetragonal structural distortion. No specific conclusions have been reached concerning the origin of the anomalous expansion for V3Ge.
KeywordsThermal Expansion Linear Thermal Expansion Gruneisen Parameter Thermal Expansion Measurement Anharmonic Potential
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