Large "forbidden" change in elastic modulus at the superconducting transition of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Y</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ba</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>9</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>
H. MathiasCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306W. G. MoultonCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306H. K. NgCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306Shaoming PanCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306Kok-Kwei PanCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306L.H. PeirceCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306L. R. TestardiCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306R. J. KennedyCenter for Materials Research and Technology, Florida State University, Tallahassee, Florida 32306
1987lv
ABI
Аннотация
The torsional modulus of ${\mathrm{Y}}_{1}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{9\ensuremath{-}x}$, measured by the composite oscillator method, shows a softening of \ensuremath{\simeq}1% on cooling through the superconducting transition. The change is 3 to 4 orders of magnitude larger than that in an average modulus for a typical superconductor. For the high symmetry implied by our polycrystalline sample, furthermore, no change is allowed by symmetry for this mode at the superconducting (or any Landau-type) transition. The decrease in modulus is accompanied by an increase in damping.
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