A. Sedda | Searcharxiv

arXiv2026

Hydrostatic pressure effect on the pseudogap in Y0.77Pr0.23Ba2Cu3O7-\delta single crystals

We studied the changes of resistivity $\rho(T)$, superconducting transition temperature $T_c$, fluctuation conductivity $\sigma'(T)$, and pseudogap $\Delta^*(T)$ of $Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}$ (YPrBCO) ($x = 0.23$) single crystal under hydrostatic pressure (HP) up to $\sim 1.1$ GPa. Defects created by magnetic inclusions of $PrBa_2Cu_3O_{7-\delta}$ (PrBCO) were found to play a significant role in the behavior of the sample. The largest decrease in $\rho(T)$ was found depending on HP at a rate of $d\ln\rho(100~K)/dP = -(29 \pm 0.2) \% \cdot GPa^{-1}$. This indicates that the mechanisms of the influence of HP on the $\rho(T)$ and $T_c$ of YPrBCO and $YBa_2Cu_3O_{7-\delta}$ single crystals are different. From the analysis of the pseudogap, it was revealed that the mechanism of the interaction of charge carriers with magnetic PrBCO impurities changes three times with increasing HP. Relatively low HP, up to $\sim 0.5$ GPa, promotes the formation of defects caused by PrBCO magnetic inclusions. Starting from 0.6 GPa, the HP neutralizes the influence of magnetic impurities, and the magnetic maximum on $\Delta^*(T)$ disappears. Above $\sim 1.0$ GPa, HP aligns the magnetic moments of PrBCO, and the magnetic maximum reappears on $\Delta^*(T)$, more pronounced than at $P = 0$.

cond-mat.supr-con↗

arXiv2025

Effect of a magnetic field up to 9 T on the temperature dependence of the pseudogap in YBa$_2$Cu$_3$O$_{7-\delta}$ films

The work analyzes the effect of a magnetic field $B$ directed along the $c$ axis ($B \parallel c$) up to 9~T on the resistivity $\rho(T)$, fluctuation conductivity (FLC) $\sigma'(T)$ and pseudogap $\Delta^*(T)$ in thin films of YBa$_2$Cu$_3$O$_{7-\delta}$ with a critical temperature of the superconducting transition $T_c = 88.8$~K. In contrast to previous work, where the magnetic field was directed along the $ab$ plane ($B \parallel ab$), the influence of the field on the sample is stronger due to the contribution of both spin--orbit and Zeeman effects. It was found that the BEC--BCS transition temperature, $T_{\mathrm{pair}}$, which corresponds to the maximum of the $\Delta^*(T)$ dependence, shifts to the region of lower temperatures with increasing $B$, and the maximum value of $\Delta^*(T_{\mathrm{pair}})$ decreases in fields $B > 5$~T. It was found that with increasing field, the low-temperature maximum near $T_0$ is smeared and disappears at $B > 1$~T. In addition, above the Ginzburg temperature $T_G$, for $B > 1$~T, a minimum appears on $\Delta^*(T)$ at $T_{\min}$, which becomes very pronounced with a subsequent increase in $B$. As a result, the overall value of $\Delta^*(T_G)$ decreases noticeably, most likely due to the pair-breaking effect. At the same time, $\Delta T_{\mathrm{fl}}$ and $\xi_c(0)$ increase sharply by approximately 3 times with increasing $B$ above 1~T. Our results confirm the possibility of the formation of a vortex state in YBa$_2$Cu$_3$O$_{7-\delta}$ by a magnetic field and its evolution with increasing $B$.

cond-mat.supr-con↗