Figure 3: Third harmonic response in La1.675Eu0.2Sr0.125CuO4.
From: Unconventional charge order in a co-doped high-Tc superconductor
The nonlinear conductivity σ3 is shown in dependence on temperature and normalized to the low-temperature value (circles), with the electric fields in the CuO2 planes. Error bars are s.d. from measurements at different electric fields (see Methods). A sharp peak is observed at the intermediate phase transition temperature TEN, in good agreement with nucelar quadrupole resonance wipeout measurements (squares; error bars are s.d. of the spin–spin decay exponential least-square fits). The linear conductivity is featureless in the entire temperature range. Solid lines are a guide to the eye. The nonlinear signal closely follows the charge-stripe peak intensity (diamonds) obtained in a resonant X-ray study30 below TCO, but not at higher temperatures. This implies that the unconventional phase between TCO and TEN is qualitatively different from charge stripes and does not break translational symmetry.
