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M. Buzzi, D. Nicoletti, S. Fava, Gregor Jotzu, Kazuya Miyagawa, Kazushi Kanoda, Alyssa Henderson, Theo Siegrist, J. A. Schlueter, M.-S. Nam, Arzhang Ardavan, A. Cavalleri
Abstract
Resonant optical excitation of certain molecular vibrations in $\ensuremath{\kappa}\text{\ensuremath{-}}(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF}{)}_{2}\mathrm{Cu}[\mathrm{N}(\mathrm{CN}{)}_{2}]\mathrm{Br}$ has been shown to induce transient superconductinglike optical properties at temperatures far above equilibrium ${T}_{c}$. Here, we report experiments across the bandwidth-tuned phase diagram of this class of materials, and study the Mott insulator $\ensuremath{\kappa}\text{\ensuremath{-}}(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF}{)}_{2}\mathrm{Cu}[\mathrm{N}(\mathrm{CN}{)}_{2}]\mathrm{Cl}$ and the metallic compound $\ensuremath{\kappa}\text{\ensuremath{-}}(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF}{)}_{2}\mathrm{Cu}(\mathrm{NCS}{)}_{2}$. We find nonequilibrium photoinduced superconductivity only in $\ensuremath{\kappa}\text{\ensuremath{-}}(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF}{)}_{2}\mathrm{Cu}[\mathrm{N}(\mathrm{CN}{)}_{2}]\mathrm{Br}$, indicating that the proximity to the Mott insulating phase and possibly the presence of preexisting superconducting fluctuations are prerequisites for this effect.