Hydrostatic-pressure effects on the pseudogap in slightly doped YBa₂Cu₃O_7−δ single crystals

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• 作者：A.L. Solovjov^a ; ^b ; L.V. Omelchenko^a ; ^b ; R.V. Vovk^c ; O.V. Dobrovolskiy^c ; ^d ; ^{Dobrovolskiy@Physik.uni-frankfurt.de" class="auth_mail" title="E-mail the corresponding author} ; Z.F. Nazyrov^c ; S.N. Kamchatnaya^c ; D.M. Sergeyev^e
• 关键词：Superconducting cuprates ; Pseudogap ; Electrical resistance measurements
• 刊名：Physica B: Physics of Condensed Matter
• 出版年：2016
• 出版时间：15 July 2016
• 年：2016
• 卷：493
• 期：Complete
• 页码：58-67
• 全文大小：1864 K

文摘

The influence of hydrostatic pressure P up to 1.05 GPa on resistivity ρ  , excess conductivity σ^′(T)${\sigma }^{\prime }\left(T\right)$ and pseudogap Δ^⁎(T)${\Delta }^{⁎}\left(T\right)$ is investigated in slightly doped single crystals of YBa₂Cu₃O_7−δ ($T_c(P=0)\approx 49.2\mathrm{K}$ and δ≈0.5$\delta \approx 0.5$). The critical temperature T_c is found to increase with increasing pressure at a rate ${\mathit{dT}}_c/\mathit{dP}=+5.1{\mathrm{KGPa}}^{-1}$, while $\rho \left(300\mathrm{K}\right)$ decreases at a rate $d\ln \rho /\mathit{dP}=(-19\pm 0.2)\%{\mathrm{GPa}}^{-1}$. Near T_c, independently on pressure, σ^′(T)${\sigma }^{\prime }\left(T\right)$ is well described by the Aslamasov–Larkin and Hikami–Larkin fluctuation theories, demonstrating a 3D–2D crossover with increase of temperature. The crossover temperature T₀ determines the coherence length along the c  -axis ${\xi }_c\left(0\right)\simeq (3.43\pm 0.01)\mathring{\mathrm{A}}$ at P=0, which is found to decrease with increasing P  . At the same time, Δ^⁎${\Delta }^{⁎}$ and the BCS ratio $2{\Delta }^{⁎}/k_B{T}_c$ both increase with increasing hydrostatic pressure at a rate $d\ln {\Delta }^{⁎}/\mathit{dP}\approx 0.36{\mathrm{GPa}}^{-1}$, implying an increase of the coupling strength with increasing P. At low temperatures below T_pair, the shape of the Δ^⁎(T)${\Delta }^{⁎}\left(T\right)$ curve is found to be almost independent of pressure. At high temperatures, the shape of the Δ^⁎(T)${\Delta }^{⁎}\left(T\right)$ curve changes noticeably with increasing P, suggesting a strong influence of pressure on the lattice dynamics. This unusual behavior is observed for the first time.