Effect of Pressure on the Pseudogap in Bi2223: Cuprates Are Not Strongly Coupled Superconductors
A. I. D’yachenko$^{1}$, V. Yu. Tarenkov$^{2}$, V. V. Kononenko$^{2}$, E. M. Rudenko$^{1}$
$^{1}$G.V. Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky Blvd., UA-03680 Kyiv-142, Ukraine
$^{2}$Donetsk Institute for Physics and Engineering Named after O.O. Galkin, NAS of Ukraine, 46 Nauky Ave., UA-03680 Kyiv, Ukraine
Received: 09.12.2015. Download: PDF
The Andreev and tunnelling spectroscopy methods show that hydrostatic pressure ($P$) enhances $T_c$ with $dln(T_{c})/dP = (1,5 \pm 0,3)\cdot10^{-3}$ kbar$^{-1}$ and energy gap $\Delta_{0}$ with $dln(\Delta_{0})/dP = (4,5 \pm 0,5)\cdot10^{-3}$ kbar$^{-1}$ for the optimally doped Bi$_{1.6}$Pb$_{0.4}$Sr$_{1.8}$Ca$_{2.2}$Cu$_{3}$O$_{x}$ cuprate (Bi2223, $T_{c}$ $\cong$ 110—112 К). The observed increase of ratio $2\Delta_{0}/(kT_{c})$ due to pressure is explained by the increase of the pseudogap $\Delta_{PG} (dln(\Delta_{PG})/dP = (4,5 \pm 0,5)\cdot10^{-3}$ kbar$^{-1}$), but not conditioned by increasing electron—boson coupling. The obtained results show that the anomalously large ratio $2\Delta_{0}/(kT_{c}) \geq 8-9$ for optimally doped cuprates is explained by the influence of the pseudogap, but not effective coupling of electrons with low-frequency bosons.
Key words: pseudogap, doped cuprates, energy gap, electron—boson coupling.
URL: http://mfint.imp.kiev.ua/en/abstract/v38/i05/0565.html
DOI: https://doi.org/10.15407/mfint.38.05.0565
PACS: 74.20.Fg, 74.25.Kc, 74.50.+r, 74.55.+v, 74.62.Fj, 74.72.-h, 74.72.Kf
Citation: A. I. D’yachenko, V. Yu. Tarenkov, V. V. Kononenko, and E. M. Rudenko, Effect of Pressure on the Pseudogap in Bi2223: Cuprates Are Not Strongly Coupled Superconductors, Metallofiz. Noveishie Tekhnol., 38, No. 5: 565—599 (2016) (in Russian)