Abstract-Possible light-induced superconductivity in K3C60 at high temperature

• M. Mitrano,
• A. Cantaluppi,
• D. Nicoletti,
• S. Kaiser,
• A. Perucchi,
• S. Lupi,
• P. Di Pietro,
• D. Pontiroli,
• M. Riccò,
• S. R. Clark,
• D. Jaksch
• & A. Cavalleri

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature16522.html

The non-equilibrium control of emergent phenomena in solids is an important research frontier, encompassing effects such as the optical enhancement of superconductivity¹. Nonlinear excitation^2, 3 of certain phonons in bilayer copper oxides was recently shown to induce superconducting-like optical properties at temperatures far greater than the superconducting transition temperature, Tc(refs 4, 5, 6). This effect was accompanied by the disruption of competing charge-density-wave correlations^7, 8, which explained some but not all of the experimental results. Here we report a similar phenomenon in a very different compound, K3C60. By exciting metallic K3C60 with mid-infrared optical pulses, we induce a large increase in carrier mobility, accompanied by the opening of a gap in the optical conductivity. These same signatures are observed at equilibrium when cooling metallic K3C60 below Tc (20 kelvin). Although optical techniques alone cannot unequivocally identify non-equilibrium high-temperature superconductivity, we propose this as a possible explanation of our results.

Macroscopic non-classical states and terahertz quantum processing in room-temperature diamond

http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2011.296.html
The nature of the transition between the familiar classical, macroscopic world and the quantum, microscopic one continues to be poorly understood. Expanding the regime of observable quantum behaviour to large-scale objects is therefore an exciting open problem¹. In macroscopic systems of interacting particles, rapid thermalization usually destroys any quantum coherence before it can be measured or used at room temperature². Here, we demonstrate quantum processing in the vibrational modes of a macroscopic diamond sample under ambient conditions. Using ultrafast Raman scattering, we create an extended, highly non-classical state in the optical phonon modes of bulk diamond. Direct measurement of phonon coherence and correlations establishes the non-classical nature of the crystal dynamics. These results show that optical phonons in diamond provide a unique opportunity for the study of large-scale quantum behaviour, and highlight the potential for diamond as a micro-photonic quantum processor capable of operating at terahertz rates.