title: Effects of pressure and distortion on superconductivity in Tl₂Ba₂CaCu₂O(8+δ).
abstract: The systematic evolution of the structural, vibrational, and superconducting properties of nearly optimally doped Tl2Ba2CaCu2O(8+δ) with pressure up to 30 GPa is studied by x-ray diffraction, Raman scattering, and magnetic susceptibility measurements. No phase transformation is observed in the studied pressure regime. The obtained lattice parameters and unit-cell volume continuously decrease with pressure by following the expected equation of state. The axial ratio of c/a exhibits an anomaly starting from 9 GPa. At such a pressure level, the deviation from the nonlinear variation of the phonon frequencies is detected. Both the above observations indicate the enhancement of the distortion upon compression. The superconducting transition temperature is found to exhibit a parabolic behavior with a maximum of 114 K around 7 GPa. We demonstrate that the interplay between the intrinsic pressure variables and distortion controls the superconductivity.
authors.affiliation: Department of Physics, South China University of Technology, Guangzhou 510640, People's Republic of China. Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, People's Republic of China. Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.
authors.forename: Jian-Bo
authors.initials: JB
authors.lastname: Zhang
authors.forename: Viktor V
authors.initials: VV
authors.lastname: Struzhkin
authors.forename: Wenge
authors.initials: W
authors.lastname: Yang
authors.forename: Ho-Kwang
authors.initials: HK
authors.lastname: Mao
authors.forename: Hai-Qing
authors.initials: HQ
authors.lastname: Lin
authors.forename: Yong-Chang
authors.initials: YC
authors.lastname: Ma
authors.forename: Nan-Lin
authors.initials: NL
authors.lastname: Wang
authors.forename: Xiao-Jia
authors.initials: XJ
authors.lastname: Chen