C. M. Duffy | Searcharxiv

arXiv2025

Charge order in the Pr substituted YBa$_2$Cu$_3$O$_7$ from high-field Hall effect measurements

The mechanism of doping in the composite Pr$_x$Y$_{1-x}$Ba$_2$Cu$_3$O$_{7-\delta}$ (Pr-YBCO) system is distinct from that of pure YBCO, offering a means to explore the requirements for the numerous electronic orders appearing in the phase diagram. One such example is the ubiquitous 2D charge order and concomitant Fermi surface reconstruction in underdoped YBCO. Here, using magnetotransport and Hall effect measurements, we find signatures of a Fermi surface reconstruction similar to that in pure YBCO indicating the presence of 2D charge order in Pr-YBCO. Additionally, we find that the phase diagrams of Pr-YBCO and YBCO are decidedly symmetric despite the additional disorder in the former and the distinction between hole depletion through Pr substitution and through O reduction. This indicates that while the mechanism of doping differs, the amount of charge carriers in the planes is the most important factor governing the electronic orders in these systems.

cond-mat.supr-con↗

arXiv2025

Evidence for spin-fluctuation-mediated superconductivity in electron-doped cuprates

In conventional, phonon-mediated superconductors, the transition temperature $T_c$ and normal-state scattering rate $1/τ$ - deduced from the linear-in-temperature resistivity $ρ(T)$ - are linked through the electron-phonon coupling strength $λ_{\rm ph}$. In cuprate high-$T_c$ superconductors, no equivalent $λ$ has yet been identified, despite the fact that at high doping, $α$ - the low-$T$ $T$-linear coefficient of $ρ(T)$ - also scales with $T_c$. Here, we use dc resistivity and high-field magnetoresistance to extract $τ^{-1}$ in electron-doped La$_{2-x}$Ce$_x$CuO$_4$ (LCCO) as a function of $x$ from optimal doping to beyond the superconducting dome. A highly anisotropic inelastic component to $τ^{-1}$ is revealed whose magnitude diminishes markedly across the doping series. Using known Fermi surface parameters and subsequent modelling of the Hall coefficient, we demonstrate that the form of $τ^{-1}$ in LCCO is consistent with scattering off commensurate antiferromagnetic spin fluctuations of variable strength $λ_{\rm sf}$. The clear correlation between $α$, $λ_{\rm sf}$ and $T_c$ then identifies low-energy spin-fluctuations as the primary pairing glue in electron-doped cuprates. The contrasting magnetotransport behaviour in hole-doped cuprates suggests that the higher $T_c$ in the latter cannot be attributed solely to an increase in $λ_{\rm sf}$. Indeed, the success in modelling LCCO serves to reinforces the notion that resolving the origin of high-temperature superconductivity in hole-doped cuprates may require more than a simple extension of BCS theory.

cond-mat.supr-con↗