Materials Research and Technology

Biography

Biography: Masayuki Suda

Abstract

Recently, electric-double-layers (EDL) of ionic liquids with huge capacitance have been employed in superconducting field-effect transistors as a nano-gap capacitor. However, due to the freezing of the ionic motions below ~200 K, modulations of the carrier density so far have been limited to the high-temperature regime. In this study, we fabricated novel photo-active superconducting devices by laminating a single crystal of κ-(BEDT-TTF)2Cu[N(CN)t]Br on the substrates coated with self-assembled monolayer of spyropiran-derivatives (SP-SAM). The initial resistances for the devices showed Mott insulator phase in the resistance measurements. After UV irradiation, however, superconducting transition was clearly observed. This photo-induced superconducting phase remained even after the irradiation was stopped. The resistance recovered to nearly the initial value by visible light irradiation, showing a reversible switching capability. From our previous measurements, κ-Br is known to evoke superconductivity by electrostatic carrier doping. The above reversible switching of superconductivity should also be due to a carrier doping by the formation of EDL at the interface. Indeed, spyropirans can switch between a non-ionic isomer and a zwitterionic isomer when triggered by light-irradiation with different wavelengths, resulting in a significant change in the electric dipole moment. Reversible changes in dipole moment of SP-SAM produced two distinct electric fields between the κ-Br and the substrates that created electrostatically doped carriers. Thus, superconductivity could be switched by photo-irradiation by photo-induced EDL formation. This result opens new possibilities for the novel electronics utilizing a photo-active electric double layer which can modulate electric-fields by light irradiation.

Recent Publications

1. Suda M et al. N-type superconductivity in an organic Mott insulator induced by light-driven electron-doping. (2016) submitted.
2. Suda M, Kato R, Yamamoto HM (2015) Light-induced superconductivity using a photoactive electric double layer. Science 347:743-746.
3. Suda M et al. (2014) Strain-tunable superconducting field-effect transistor with an organic strongly-correlated electron system. Advanced Materials 26:3490-3495.
4. Yamamoto HM, Suda M et al. (2013) A strained organic field-effect transistor with a gate-tunable superconducting channel. Nature Communications 4:2379.
5. Tajima N, Suda M et al. (2013) Quantum Hall effect in multilayered massless Dirac fermion systems with tilted cones. 88:075315.