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 breakdown. Here we report electric-field-induced superconductivity in an insulator by using an electric-double-layer gating in an organic electrolyte. Sheet carrier density was enhanced from zero to 10(14) cm(-2) by applying a gate voltage of up to 3.5 V to a pristine SrTiO(3) 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 crystals, indicating this method as promising for searching for unprecedented superconducting states.

Superconductivity at interfaces has been investigated since the first demonstration of electric-field-tunable superconductivity in ultrathin films in 1960(1). So far, research on interface superconductivity has focused on materials that are known to be superconductors in bulk. Here, we show that electrostatic carrier doping can induce superconductivity in KTaO(3), a material in which superconductivity has not been observed before. Taking advantage of the large capacitance of the self-organized electric double layer that forms at the interface between an ionic liquid and KTaO(3) (ref. 12), we achieve a charge carrier density that is an order of magnitude larger than the density that can be achieved with conventional chemical doping. Superconductivity emerges in KTaO(3) at 50 mK for two-dimensional carrier densities in the range 2.3 × 10(14) to 3.7 × 10(14) cm(-2). The present result clearly shows that electrostatic carrier doping can lead to new states of matter at nanoscale interfaces.

We report the pressure-induced superconductivity in the noncentrosymmetric heavy-fermion CeRhSi3. The superconductivity emerges above about 12 kbar even though the antiferromagnetic ordering persists. Furthermore, another anomaly is observed in the superconducting phase. The anomalous magnetic field-temperature phase diagram with a high upper critical field suggests that an unconventional superconductivity is realized in CeRhSi3.

The temperature dependence of the 195 Pt Knight shift, K, for the high quality single crystal UPt 3 has been measured down to T 28 mK in applied magnetic fields parallel and perpendicular to the hexagonal c axis. No change of K's has been found across the superconducting transition temperature T c down to 28 mK regardless of the crystal directions and independent of the superconducting multiphases. It is demonstrated that UPt 3 is the odd-parity superconductor with parallel spin pairing following the direction of the magnetic field in a range of 4.4 -15.6 kOe without an appreciable pinning of the order parameter to the lattice. [S0031-9007(96)

195 Pt Knight shift (KS) measurements covering the superconducting multiple phases for major field (H) orientations have been carried out on the high-quality single crystal UPt 3 . For H . 5 kOe, the KS does not change below the superconducting transition temperature T c down to 28 mK, regardless of major crystal orientations, which provides evidence that the odd-parity superconductivity with the parallel spin pairing is realized. By contrast, the KS decreases below T c for H b k b axis and H b , 5 kOe and for H c k c axis and H c , 2.3 kOe, whereas the KS for H a k a axis is T independent across T c down to H a ϳ 1.764 kOe. These novel findings entitle UPt 3 as the first spin-triplet oddparity superconductor including a nonunitary pairing characterized by the two-component d vector like d b 1 id c at low T and low H. [S0031-9007(98)