Evidence for unusual superconducting correlations coexisting with stripe order in ${\text{La}}_{1.875}{\text{Ba}}_{0.125}{\text{CuO}}_4$

We present new x-ray and neutron-scattering measurements of stripe order in ${\text{La}}_{1.875}{\text{Ba}}_{0.125}{\text{CuO}}_4$, along with low-field susceptibility, thermal conductivity, and specific-heat data. We compare these with previously reported results for resistivity and thermopower. Temperature-dependent features indicating transitions (or crossovers) are correlated among the various experimental quantities. Taking into account recent spectroscopic studies, we argue that the most likely interpretation of the complete collection of results is that an unusual form of two-dimensional superconducting correlations appears together with the onset of spin-stripe order. Recent theoretical proposals for a sinusoidally modulated superconducting state compatible with stripe order provide an intriguing explanation of our results and motivate further experimental tests. We also discuss evidence for one-dimensional pairing correlations that appear together with the charge order. With regard to the overall phenomenology, we consider the degree to which similar behavior may have been observed in other cuprates and describe possible connections to various puzzling phenomena in cuprate superconductors.

Figure 1

(Color online) (a) Temperature dependence of normalized peak intensities of the charge-order peak $\left(2+2ϵ,0,5.5\right)$ (filled circles) and the LTT superlattice peak (1,0,0) (diamonds) obtained by 100 keV x-ray diffraction; transverse width of the charge-order peak indicated by open circles. Lines through the data points are guides for the eyes. (b) Normalized peak intensity (filled circles) and transverse width (open circles) of the magnetic peak $\left(0.5-ϵ,0.5,0\right)$ measured by neutron diffraction with a neutron energy of 5 meV. (c) $\mathbf{Q}$ integrated ${\chi }^{″}\left(\omega \right)$ for $\hslash \omega =0.5\text{meV}$ (squares) and 1.5 meV (circles). Lines through the data are guides for the eyes. Vertical lines in all panels denote transition temperatures, as discussed in the text.

Figure 2

(Color online) $Q$-integrated dynamic susceptibility vs energy for incommensurate magnetic fluctuations. Circles, diamonds, and squares represent results obtained at $T=46$, 30, and 5 K, respectively. The dashed lines, which are effectively guides for the eyes, are explained in the text.

Figure 3

(Color online) (a) In-plane resistivity, ${\rho }_{ab}$ (circles), and resistivity perpendicular to the planes, ${\rho }_c$, divided by ${10}^3$ (squares). (b) Magnetic susceptibility measured with the field perpendicular to the planes and (c) parallel to the planes for an applied field of 2 Oe. $\chi$ has been corrected for shape anisotropy and the offsets (to allow plotting on a logarithmic scale) are $4\pi {\chi }_{\perp }\left(60\text{K}\right)=4.2\times {10}^{-4}$ and $4\pi {\chi }_{\parallel }\left(60\text{K}\right)=1.6\times {10}^{-5}$. Vertical gray lines denote relevant temperatures, with labels at the top.

Figure 4

(Color online) (a) Thermoelectric power measured parallel to the planes, $S_{ab}$. Inset shows portion of data on an expanded scale. (b) Thermal conductivity, ${\kappa }_{ab}$. (c) Specific heat, $C$, divided by temperature. Relevant temperatures are indicated by vertical gray lines.

Figure 5

(Color online) Specific heat divided by temperature, plotted vs $T^2$. Measurements in $c$-axis magnetic fields of 0 and 9 T represented by circles and squares, respectively. Extrapolations of the fitted lines to $T=0$ provide estimates of $\gamma \left(T\to 0\right)$ given in the text.

Figure 6

(Color online) Temperature dependence of the planar and $c$-axis resistivity vs temperature replotted on a linear scale. The dashed lines correspond to ${\rho }_{ab}=a_0+a_1{T}^{{\alpha }_{ab}}$ with ${\alpha }_{ab}=1$ and $a_0=0.059\text{m}\Omega \text{cm}$ and ${\rho }_c=a_3{T}^{-{\alpha }_c}$ with ${\alpha }_c=2.25$.