N-Type Superconductivity in an Organic Mott Insulator Induced by Light-Driven Electron-Doping

The presence of interface dipoles in self-assembled monolayers (SAMs) gives rise to electric-field effects at the device interfaces. SAMs of spiropyran derivatives can be used as photoactive interface dipole layer in field-effect transistors because the photochromism of spiropyrans involves a large dipole moment switching. Recently, light-induced p-type superconductivity in an organic Mott insulator, κ-(BEDT-TTF)₂Cu[N(CN)₂]Br (κ-Br: BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) has been realized, thanks to the hole carriers induced by significant interface dipole variation in the spiropyran-SAM. This report explores the converse situation by designing a new type of spiropyran monolayer in which light-induced electron-doping into κ-Br and accompanying n-type superconducting transition have been observed. These results open new possibilities for novel electronics utilizing a photoactive SAMs, which can design not only the magnitude but also the direction of photoinduced electric-fields at the device interfaces.

Light-induced superconductivity in an organic Mott insulator is realized by light-driven electron doping. This effect can be attributed to photoinduced built-in potential formation in a photochromic-spiropyran monolayer. The polarity of photoinduced mobile carriers can be systematically controlled by designing the dipole moment variation of the spiropyran monolayers.

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