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www.sciencemag.org/cgi/content/full/331/6014/189/dc1 Supporting Online Material for Light-Induced Superconductivity in a Stripe-Ordered Cuprate D. Fausti,* R. I. Tobey, N. Dean, S. Kaiser, A.

1 Supporting Online Material for Light-Induced Superconductivity in a Stripe-Ordered Cuprate D. Fausti,* R. I. Tobey, N. Dean, S. Kaiser, A. Dienst, M. C. Hoffmann, S. Pyon, T. Takayama, H. Takagi, A. Cavalleri* *To whom correspondence should be addressed. andrea.cavalleri@mpsd.cfel.de (A.C.); daniele.fausti@mpsd.cfel.de (D.F.) This PDF file includes: Materials and Methods Figs. S1 to S3 Published 14 January 2011, Science 331, 189 (2011) DOI: /science

2 SUPPORTING ONLINE MATERIAL Materials and Methods Sample. Single crystals of La Eu 0.2 Sr CuO 4 were grown using a traveling solvent floating zone technique, confirmed to be non-superconducting above 5 K by resistivity and magnetization measurements. Hard X-ray diffraction and Hall coefficient measurements evidence the appearance of the static stripe ordering below 80 K. Equilibrium broadband optical constants of LESCO 1/8. The equilibrium optical constants for LESCO 1/8 were calculated by Kramers Kroening transformations of broadband reflectivities, in and out of plane (see figure S1a). Outside of the measured range the in-plane reflectivity (black dots) was extrapolated at low energy by a Drude model and by a quadratically decreasing reflectivity on the high-energy side. The out-ofplane reflectivity was approximated at low frequency by a parabolic function, joining the FTIR measurements (red) with time domain THz spectroscopy (blue). Fig S1 (a) Static reflectivity of LESCO 1/8, measured with a combination of FTIR and Time domain THz spectroscopy. (b) Extinction coefficient for light polarized in (black) and orthogonal to the planes (red). Note that a correction to the THz measurements has been introduced to take into account the different incidence angles, in the FTIR measurements (normal incidence) and the time domain THz measurements (45 degree angle of incidence). Fig.1(b) reports the extinction

3 coefficient α, for two polarizations. The extinction depth (1/α) of the 16-µm pump pulses is at least 50 times smaller than that of the probing THz field. Transient THz response (LESCO 1/8 ): Femtosecond pulses of 35-fs duration at 800-nm wavelength were generated by an amplified Ti:Sapphire laser, delivering ~2mJ energy at 1KHz repetition rate. THz radiation was generated by optical rectification in a ZnTe crystal. The THz pulses reflected by the sample surface were measured through Electro Optic Sampling (EOS) of the THz fields with 800nm pulses. All the experiments were performed in a vacuum chamber containing THz generation, delivery to the sample and pick up optics. This avoided the use of windows in the cryostat, and maximized the available pump and probe flux. Mid-IR pump pulses of 2µJ energy were generated by different frequency generation (DFG) between the signal and the idler from an optical parametric amplifier OPA. The spectrum of the NIR pulses generated was measured with a linear interferometer equipped with a Mercury Cadmium Tellurite detector. The absolute equilibrium THz reflectivity was obtained by comparing the measured field reflectance of the sample with that of a gold film deposited on the sample surface. To derive the changes in the conductivity of the photo-excited layer ( "# ) from the changes in the reflected field ΔE/E, we considered a thin photo-excited layer and a semiinfinite unperturbed bulk sample beneath. Making use of a thin film approximation the perturbed layer as following: (S1) where is the frequency dependent pump-induced changes in conductivity at time delay, is the vacuum permittivity, is the thickness of the layer, and is the complex refractive index of the unperturbed material. Two main contributions to the transient conductivity are found, a flat negative response and a 1/ω dependent contribution at low frequency. See figure M2. The flat contribution can be fitted by a photo-induced shift of an oscillator at high energy. The c-axis low optical constants are

4 dominated by the presence of phonon modes at about 250cm -1. Photo-excitation of the 600cm -1 mode will result in a strong perturbation of the lower energy modes and in a frequency independent shift of the conductivity at frequencies below 100cm -1. Fig S2: The transient imaginary part of the conductivity for different time delays. The transient response exhibits two responses: a negative flat background and a 1/ω positive component at low frequency. Photo-susceptibility. We note that the amplitude of the experimental signal scales as ln(f), where F is the fluence of the pump. This is evidenced by the linear dependence of the signal in the semi-log plot of figure S3. This is for two reasons. First, in the plane parallel to the optical surface of the sample, the fluence profile of the excitation beam has a Gaussian dependence on the radial coordinate r, scaling as F(x) = F 0 e r 2 /σ 2 (where r is the distance from the centre of the beam and σ is its width). Above a fluence value F sat the optical constants reach a saturation value characteristic of the superconducting phase and remain unchanged if the fluence is increased further. This implies that for F>F sat, one can define a radius r sat such that the reflectivity change ΔR = ΔR sat for all r<r sat. This leads to a signal scaling ΔR(F) that is proportional to σ 2 ln(f/f sat ), as discussed in J.M. Liu Opt. Lett. 7, 192 (1982). We note that σ is a function of wavelength, since each set of measurements is obtained after a different optimization of the optical parametric amplifier. Thus the slope of the logarithmic growth varies for different excitation wavelengths.

5 Second, in direction perpendicular to the surface, the pump fluence scales like F(x) = F0e αz, implying that for F>Fsat one can define a depth zsat such that the reflectivity change ΔR = ΔRsat for all z<zsat. This leads to a signal scaling ΔR(F) that is again proportional to ln(f/fsat). For the purposes of this paper, we define an operational photo-susceptibility given by 1/Fsat, which gives a quantitative estimate of the fluence at which the sample is locally turned superconducting. In figure S3, we plot the logarithmic scaling of the signal for different pump wavelengths, and 1/Fsat(λ), where λ is the pump wavelength in microns. A clear resonance near 15 microns is observed. Fig S3: Amplitude of the JPR signal as a function of fluence (left graph). The zeroamplitude-signal intercept gives the threshold. The inverse threshold is plotted as a function of wavelength, providing an operational description of the photo-susceptibility.

Optically enhanced coherent transport in YBa 2 Cu 3 O 6.5 by ultrafast redistribution of interlayer coupling

Optically enhanced coherent transport in YBa 2 Cu 3 O 6.5 by ultrafast redistribution of interlayer coupling W. Hu 1*, S. Kaiser 1*, D. Nicoletti 1*, C.R. Hunt 1,4*, I. Gierz 1, M. C. Hoffmann 1, M. Le