Time-resolved optical reflectivity of the electron-doped Nd2-xCexCuO4 + \delta cuprate superconductor: Evidence for an interplay between competing orders
J. P. Hinton, J. D. Koralek, G. Yu, E. M. Motoyama, Y. M. Lu, A. Vishwanath, M. Greven, and J. Orenstein
Accepted
We use pump-probe spectroscopy to measure the photoinduced reflectivity $\Delta R$ of the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_{x}$CuO$_{4+\delta}$ at a value of $x$ near optimal doping, as a function of time, temperature, and laser fluence. We observe the onset of a negative $\Delta R$ signal at $T^{*} \approx 75$~K, above the superconducting transition temperature, $T_{c}$, of 23 K. The relatively slow decay of $\Delta R$, compared to the analogous signal in hole doped compounds, allows us to resolve time-temperature scaling consistent with critical fluctuations. A positive $\Delta R$ signal onsets at $T_{c}$ that we associate with superconducting order. We find that the two signals are strongly coupled below $T_{c}$, in a manner that suggests a repulsive interaction between superconductivity and another fluctuating order.