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

TL;DR

This work investigates how Pr substitution in YBa$_2$Cu$_3$O$_{7-\delta}$ tunes hole doping and disorder, and whether it preserves the 2D charge-order–driven Fermi surface reconstruction seen in YBCO. Using high-field magnetotransport and Hall effect measurements up to $65$ T on Pr-YBCO crystals with $x=0.2$–$0.45$, the authors identify a Hall sign change at a temperature $T_0$ that shifts with Pr content, signaling FSR due to charge order and an electron pocket in the reconstructed Fermi surface. The Pr-YBCO phase diagram is qualitatively similar to YBCO, but the competition between charge order and superconductivity is weaker, likely because of disorder and shorter CO coherence lengths; the work also discusses the potential presence of 3D CO in Pr-YBCO, though evidence remains inconclusive. Overall, the results support the view that the in-plane carrier density, rather than the specific doping mechanism, governs the emergence of CO and FSR in cuprates, while disorder tends to smear transitions and suppress conventional CO–SC competition.

Abstract

The mechanism of doping in the composite Pr$_x$Y$_{1-x}$Ba$_2$Cu$_3$O$_{7-δ}$ (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.

Figures (6)

• Figure 1: The phase diagram of Pr-YBCO. The yellow region marks the antiferromagnetic (AFM) region bounded by $T_N$. Muon spin-relaxation measurements reveal two types of magnetic order: the suppression of the Mott state, and magnetic order from the Pr spin. The superconducting dome is marked in blue. The star (diamond) symbols correspond to $T_c$ measured by squid (resistivity) in the four Pr-YBCO samples presented in this study.
• Figure 2: $R_H(T)$ for four samples showing a change of sign at higher $T_c$. The temperature at which this occurs ($T_0$) decreases in parallel with $T_c$, eventually remaining positive for the low-$T_c$ crystals. The same behaviour is observed in the two samples which are not shown.
• Figure 3: (a) $R_H$ as a function of $\mu_0 H$ at $T = 10$ K showing quite clearly the sign change that occurs and its doping dependence in Pr-YBCO. (b) The same plot but for pure YBCO at several doping levels (from ref. LeBoeuf_PRB_2011).
• Figure 4: $R_H(T)$ normalized by its value at $T=100$ K for (a) Pr-YBCO (this work) and (b) YBCO (from ref. LeBoeuf_PRB_2011). Both show a systematic variation of $T_0$ with doping while the doping levels closest to the antiferromagnetic phase does not exhibit a sign change.
• Figure 5: $H_{\rm irr}(T\rightarrow0)$ for YBCO Grissonnanche_NatCommun_2014 (blue squares) and Pr-YBCO (red stars) as a function of $T_c$. The clear depression seen in YBCO is not observed in Pr-YBCO representing the weaker competition between charge correlations and superconductivity in the latter. A monotonic dependence of $H_{c2}(0)$ in Pr-YBCO has also been observed in a more extensive doping range in ref. Jia_PRB_1992.