Structural and phonon anomalies in the superconducting with varying doping level at high pressures

¹ Department of Physics and State Key Laboratory of Surface Physics, Fudan University - Shanghai 200438, PRC
² Center for High Pressure Science and Technology Advanced Research - Shanghai 201203, PRC
³ Condensed Matter Physics and Materials Science, Brookhaven National Laboratory - New York 11973, USA
⁴ Institute for Nuclear Research RAS - 108840, Troitsk, Moscow, Russia
⁵ A. V. Shubnikov Institute of Crystallography, Federal Scientific Research Center “Crystallography and Photonics” of RAS - 119333, Moscow, Russia
⁶ REC “Functional Nanomaterials” Immanuel Kant Baltic Federal University - 236041, Kaliningrad, Russia
⁷ Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments (MFree), Shanghai Advanced Research in Physical Sciences (SHARPS) - Pudong, Shanghai 201203, PRC
⁸ Department of Physics and Texas Center for Superconductivity, University of Houston - Houston, TX 77204, USA

Received: 18 December 2023
Accepted: 29 April 2024

Abstract

We examined the effect of the lattice compression on the crystal structure of the Bi₂Sr₂CaCu₂ superconductor with nearly optimally doped and overdoped composition using X-ray diffraction technique. Our studies show that at high pressures (up to 30 GPa ) the doping level does not affect the crystal structure of this superconductor. Along with this, structural anomalies in ratio appear at a pressure that corresponds to that at which T_c begins to decrease. This fact indicates a close connection between the observed anomalies and superconductivity. We also studied the effect of doping and pressure on the T_c(P) and on the Raman active lattice modes of the Bi₂Sr₂CaCu₂ superconductors. We find universal suppression of the T_c by the pressure starting from the critical pressure P_c in the range from 9 to 16 GPa, depending on the doping level of the Bi₂Sr₂CaCu₂ samples. Concomitantly, we observe phonon anomalies around 10 to 20 GPa, which indicate possible pressure-induced charge redistribution in BiO layers. These newly detected anomalies may be related to the changes in the electronic structure which compete with the superconductivity.