2016/05/23 by A. L. Solovjov, L. V. Omelchenko, R. V. Vovk +6
Physics and Astronomy · #Advanced Condensed Matter Physics #Condensed matter physics #Coupling (piping) #Cuprate #Doping #Electrical resistivity and conductivity #Hydrostatic pressure #Materials science #Physics #Physics of Superconductivity and Magnetism #Pseudogap #Superconductivity #Theoretical and Computational Physics #Thermodynamics #cond-mat.supr-con
paper · pdf · doi:10.1016/j.cap.2016.05.014
published as Current Applied Physics, 16, 931 (2016) · 8 pages, 7 figures
openalex publication_date 2016/05/23 · openalex created_date 2016/06/24 · arxiv created 2018/04/03 · arxiv updated 2018/04/04 · openalex updated_date 2026/08/05
The influence of the hydrostatic pressure P up to 0.95 GPa on the excess conductivity and the pseudogap Δ*(T) in optimally doped YBCO single crystals (Tc = 91.1K at ambient pressure) is investigated by electrical resistivity measurements. A pronounced enhancement of the pseudogap under pressure of dlnΔ*/dP= 0.32, which is only a factor of 1.12 smaller than in slightly doped single crystals, is revealed for the first time. This implies a somewhat more moderate increase of the coupling strength in optimally doped cuprates with increasing pressure. Simultaneously, the ratio 2Δ*(Tc)/kBTc=5 at P=0 GPa, which is typical for high-temperature superconductors with strong coupling, increases by 16% with increasing pressure. At the same time, the pressure effect on Tc is minor: dTc/dP=+0.73 K/GPa, whereas dlnρ/dP=-17% 1/GPa is comparable with that in lightly doped YBCO single crystals. This suggests that the mechanisms of the pressure effect on ρ(T) and Tc are noticeably different. Independently of pressure, near Tc, the excess conductivity is well described by the Aslamazov-Larkin (3D-AL) and 2D Hikami-Larkin fluctuation theories, exhibiting a 3D-2D crossover with increasing temperature. However, the temperature interval Tc<T<T01, in which excess conductivity obeys the classical fluctuation theories, is exceptionally narrow (~1.16 K). Nevertheless, a peculiarity at the temperature T01, up to which the wave function phase stiffness in the superconductor is maintained, is clearly observed in the dependence Δ*(T). Below T01 a fast growth of Δ*(T) is revealed for the first time. It can be associated with a sudden increase of the superfluid density, ns, that is the density of fluctuating Cooper pairs (short-range phase correlations) forming in the sample when T approaches Tc.