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Electric-field-induced superconductivity in an insulator


Electric field control of charge carrier density has long been a key technology to tune the physical properties of condensed matter, exploring the modern semiconductor industry. One of the big challenges is to increase the maximum attainable carrier density so that we can induce superconductivity in field-effect-transistor geometry. However, such experiments have so far been limited to modulation of the critical temperature in originally conducting samples because of dielectric breakdown1,2,3,4. Here we report electric-field-induced superconductivity in an insulator by using an electric-double-layer gating in an organic electrolyte5. Sheet carrier density was enhanced from zero to 1014 cm−2 by applying a gate voltage of up to 3.5 V to a pristine SrTiO3 single-crystal channel. A two-dimensional superconducting state emerged below a critical temperature of 0.4 K, comparable to the maximum value for chemically doped bulk crystals6, indicating this method as promising for searching for unprecedented superconducting states.

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Figure 1: Schematic structures and current–voltage characteristics of an electric-double-layer field-effect transistor.
Figure 2: Electrical properties of accumulated SrTiO3 surface layer.
Figure 3: Superconducting properties and electronic structure of the SrTiO3 channel under a gate bias voltage VG=3 V.
Figure 4: Gate voltage, VG, dependence of transport properties and electronic parameters deduced with the triangular-potential approximation.


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We thank S. Maekawa, M. Mori, N. Reyren, J.-M. Triscone and A. Tsukazaki for fruitful discussions.

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Correspondence to K. Ueno or M. Kawasaki.

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Ueno, K., Nakamura, S., Shimotani, H. et al. Electric-field-induced superconductivity in an insulator. Nature Mater 7, 855–858 (2008).

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