Raman study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="italic">R</mi></mrow><mrow><mn>0.5</mn></mrow></msub></mrow></math><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="normal">Pr</mi></mrow><mrow><mn>0.5</mn></mrow></msub></mrow></math><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="normal">Ba</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="normal">Cu</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mn>7</mn><mi mathvariant="normal">−</mi><mi mathvariant="normal">δ</mi></mrow></msub></mrow></math> (R=Y, rare earth)

G. Bogachev; M. Abrashev; M. Iliev; N. Poulakis; E. Liarokapis; C. Mitros; A. Koufoudakis; V. Psyharis

doi:10.1103/PhysRevB.49.12151

Raman study of $R_{0.5}$ $\Pr_{0.5}$ ${Ba}_{2}$ ${Cu}_{3}$ $O_{7 - δ}$ (R=Y, rare earth)

G. Bogachev, M. Abrashev, M. Iliev, N. Poulakis, E. Liarokapis, C. Mitros, A. Koufoudakis, and V. Psyharis

Phys. Rev. B 49, 12151 – Published 1 May 1994

Abstract

The polarized Raman scattering of the $R_{0.5}$ $\Pr_{0.5}$ ${Ba}_{2}$ ${Cu}_{3}$ $O_{7 - δ}$ series (R=La, Pr, Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm, Yb, Lu; δ∼0) which undergoes a superconductor-to-nonsuperconductor transition between R=Gd and Dy was studied. It was found that the appearance of superconductivity correlates with observation of a two-mode behavior of the R-ion-size-sensitive $B_{1 g}$ -like mode of O(2),O(3) out-of-phase vibrations. It was also established that the Ba (xx, $A_{g}$ ) phonon line is of asymmetrical (Fano) shape for all R. The origin of the Fano effect usually attributed to interference with an electronic continuum is discussed.