Scattering and Pairing in Cuprate Superconductors

Abstract

The origin of the exceptionally strong superconductivity of cuprates remains a subject of debate after more than two decades of investigation. Here we follow a new lead: The onset temperature for superconductivity scales with the strength of the anomalous normal-state scattering that makes the resistivity linear in temperature. The same correlation between linear resistivity and Tc is found in organic superconductors, for which pairing is known to come from fluctuations of a nearby antiferromagnetic phase, and in pnictide superconductors, for which an antiferromagnetic scenario is also likely. In the cuprates, the question is whether the pseudogap phase plays the corresponding role, with its fluctuations responsible for pairing and scattering. We review recent studies that shed light on this phase - its boundary, its quantum critical point, and its broken symmetries. The emerging picture is that of a phase with spin-density-wave order and fluctuations, in broad analogy with organic, pnictide, and heavy-fermion superconductors.

Figures (8)

• Figure 1: Linear resistivity and$\boldsymbol{T}_{\mathbf{c}}$ vs doping in hole-doped cuprates.
• Figure 2: Correlation between linear resistivity and$\boldsymbol{T}_{\boldsymbol{c}}$ in cuprate, organic and pnictide superconductors.
• Figure 3: Figure 5. Phase diagram of organic and pnictide superconductors. a) Temperature-pressure phase diagram of $(\mathrm{TMTSF})_{2} \mathrm{PF}_{6}$, showing a spin-density-wave (SDW) phase below $T_{\text{SDW }}$ (orange dots) and superconductivity (SC) below $T_{\mathrm{c}}$ (blue dots) [22,29]. The latter phase ends at the critical pressure $P_{\mathrm{c}}$. b) Temperature-doping phase diagram of the iron-pnictide superconductor $\mathrm{Ba}\left(\mathrm{Fe}_{1-\mathrm{x}} \mathrm{Co}_{\mathrm{x}}\right)_{2} \mathrm{As}_{2}$, as a function of nominal Co concentration $x$, showing a metallic SDW phase below $T_{\text{SDW }}$ and superconductivity below a $T_{\mathrm{c}}$ which ends at the critical doping $x_{\mathrm{c}}$ [34]. In both panels the vertical dashed line separates a regime where the resistivity $\rho(T)$ grows as $T^{2}$ (on the right) from a regime where it grows as $T+T^{2}$ (on the left). From [29].
• Figure 4: Quantum criticality in the resistivity of cuprate, organic and pnictide superconductors.
• Figure 5: Stripe order and Hall coefficient in cuprates at$\boldsymbol{p}=\mathbf{1} / \mathbf{8}$. a) Temperature dependence of charge stripe order in Eu-LSCO at $p=1 / 8$, as detected by resonant soft X-ray diffraction (data from [99]). The grey line is a guide to the eye. b) Hall coefficient vs temperature measured in $B=15 \mathrm{~T}$ for Eu-LSCO (blue, left axis; from [46]) and YBCO (red, right axis; from [68]), both at $p \approx 1 / 8$. Adapted from [42].