Superconductivity in Single-CrystallineSr1-xLaxTiO3

Suzuki, Hiroshi; Bando, Hiroshi; Ootuka, Youiti; Inoue, Isao; Yamamoto, Tetsuya; Takahashi, Kazuhiko; Nishihara, Y.

doi:10.1143/jpsj.65.1529

Cited by 120 publications

(81 citation statements)

References 14 publications

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“…La-doped SrTiO 3 samples with a reduced doping density of 1 Â 10 20 cm À3 (Fig. 4) lie in a regime where superconducting correlations are expected to be important [22,26]. In Fig.…”

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confidence: 94%

Carrier-Controlled Ferromagnetism inSrTiO3

et al. 2012

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Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO 3 films and GdTiO 3 =SrTiO 3 heterostructures, respectively. GdTiO 3 =SrTiO 3 interfaces exhibit a highdensity 2D electron gas on the SrTiO 3 side of the interface, while, for the SrTiO 3 films, carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO 3 films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO 3 =SrTiO 3 heterostructures scales with the thickness of the SrTiO 3 quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO 3 .

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“…La-doped SrTiO 3 samples with a reduced doping density of 1 Â 10 20 cm À3 (Fig. 4) lie in a regime where superconducting correlations are expected to be important [22,26]. In Fig.…”

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confidence: 94%

Carrier-Controlled Ferromagnetism inSrTiO3

et al. 2012

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“…For example, a small amount of electron doping by chemical substitution of oxygen vacancies renders the material conducting and even superconducting at low temperatures. 4,5 Light doping with electrons ͑ϳ10 19 cm −3 ͒ makes the originally insulating ST metallic because of significant screening resulting from a nearby ferroelectric instability. 6,7 Such a variety of fascinating physical properties is a strong indication that ST may have uses in the emerging field of oxide-based electronics.…”

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confidence: 99%

Structural conditions that leads to photoluminescence emission in SrTiO3: An experimental and theoretical approach

Longo

Figueiredo

Lázaro

et al. 2008

Journal of Applied Physics

159

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• ͒ vacancies were identified in disordered SrTiO 3 powders prepared by the polymeric precursor method, based on experimental measurements by x-ray absorption near edge structure spectroscopy. The paramagnetic complex states of ͓TiO 5 · V O • ͔ and ͓SrO 11 · V O • ͔ with unpaired electrons were confirmed by electron paramagnetic resonance spectroscopy. The disordered powders showed strong photoluminescence at room temperature. Structural defects of disordered powders, in terms of band diagram, density of states, and electronic charges, were interpreted using high-level quantum mechanical calculations in the density functional framework. The four periodic models used here were consistent with the experimental data and explained the presence of photoluminescence.

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“…4 This superconductivity differs from the superconductivity of bulk SrTiO 3 with T c = 300 mK in the carrier concentration and the dimensionality of mobile electrons. 5 The discovery of superconductivity is significant since it is promising to control the superconducting states electrically by the applied voltage. Controlling the number of carrier by applied voltage in superconductors is one of the intriguing issues to understand the mechanism of the superconductivity.…”

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Electrically controlled superconducting states at the heterointerfaceSrTiO3/LaAlO3

et al. 2009

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We study the symmetry of Cooper pair in a two-dimensional Hubbard model with the Rashbatype spin-orbit interaction as a minimal model of electron gas generated at a heterointerface of SrTiO3/LaAlO3. Solving theÉliashberg equation based on the third-order perturbation theory, we find that the gap function consists of the mixing of the spin-singlet dxy-wave component and the spin-triplet (px ± ipy)-wave one due to the broken inversion symmetry originating from the Rashbatype spin-orbit interaction. The ratio of the d-wave and the p-wave component continuously changes with the carrier concentration. We propose that the pairing symmetry is controlled by tuning the gate voltage.PACS numbers: 74.25.Dw, 74.78.Fk, 71.10.Fd Recent development of technology of epitaxial growth makes it possible to fabricate heterointerface between two different transition-metal oxides. 1,2 The discovery of the generation of two-dimensional electron gas (2DEG) at the n-type heterointerface SrTiO 3 /LaAlO 3 attracts much interest 3 since both SrTiO 3 and LaAlO 3 are band insulators in the bulk material. It is also noted that this 2DEG shows superconductivity with transition temperature T c = 200 mK. 4 This superconductivity differs from the superconductivity of bulk SrTiO 3 with T c = 300 mK in the carrier concentration and the dimensionality of mobile electrons. 5 The discovery of superconductivity is significant since it is promising to control the superconducting states electrically by the applied voltage. Controlling the number of carrier by applied voltage in superconductors is one of the intriguing issues to understand the mechanism of the superconductivity. In cuprates, a superconducting region is located next to an antiferromagnetic phase in an n-T phase diagram. However, in cuprate superconductors, it is not easy to tune the number of carrier by external fields such as the magnetic field or the gate voltage since the number of carrier depends on material compositions. On the other hand, the carrier number of 2DEG at the heterointerface SrTiO 3 /LaAlO 3 can be tuned by the gate voltage since the carrier is generated by the polar and unpolar nature of LaAlO 3 and SrTiO 3 , respectively. 6 Actually, electrostatically tuned superconductor-metal-insulator transition was found to be accessible. 7,8,9 When the electron correlations (Coulomb interaction) are responsible to the superconductivity, the pairing symmetry depends on the number of carrier: The spin-triplet p-wave pairing is favored at low density, 10,11,12,13,14 while on the other hand, the spin-singlet d x 2 −y 2 -wave pairing is favored near half filling. 15,16 Thus, at the heterointerface of oxides with large Coulomb interaction, the phase transition between the spin-singlet and spin-triplet states can be observed by the applied voltage.Another characteristic feature at the heterointerface is lack of the inversion symmetry along the direction perpendicular to the interface (z-axis), which induces the asymmetric spin-orbit interaction called the Rashbatype spin-orbit intera...

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Superconductivity in Single-CrystallineSr_1-xLa_xTiO₃

Cited by 120 publications

References 14 publications

Carrier-Controlled Ferromagnetism inSrTiO3

Carrier-Controlled Ferromagnetism inSrTiO3

Structural conditions that leads to photoluminescence emission in SrTiO3: An experimental and theoretical approach

Electrically controlled superconducting states at the heterointerfaceSrTiO3/LaAlO3

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