S. Kaiser, D. Nicoletti, C. R. Hunt, W. Hu, I. Gierz, H. Y. Liu, M. Le Tacon, T. Loew, D. Haug, B. Keimer, A. Cavalleri
Strong optical fields at THz frequencies, capable of dynamically deforming the crystallographic structure of a solid, are a new tuning parameter for complex condensed matter. We use mid-infrared femtosecond pulses to resonantly excite large-amplitude vibrations of the apical oxygens in underdoped YBa_{2}Cu_{3}O_{7-d}. A transient superconducting state is discovered for base temperatures far above Tc. A finite superfluid density is observed up to room temperature, evidenced by a characteristic 1/omega frequency dependence in the imaginary part of the optical conductivity sigma_2. Gapping in the real part sigma_1 and a short-lived Josephson plasma edge along the c-axis are further evidence of a light induced superconducting state. Our experiments open tantalizing prospects for optically-driven superconductivity in new regions of the cuprate phase diagram or in new materials.
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http://arxiv.org/abs/1205.4661
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