Jifeng Shao

Superconductivity with Topological Surface State in SrxBi2Se3

By intercalation of alkaline earth metal Sr in Bi2Se3, superconductivity with large shielding volume fraction (∼91.5% at 0.5 K) has been achieved in Sr0.065Bi2Se3. Analysis of the Shubnikov-de Hass oscillations confirms the half-shift expected from a Dirac spectrum, giving transport evidence of the existence of surface states. Importantly, SrxBi2Se3 superconductor is stable under air, making SrxBi2Se3 an ideal material base for investigating topological superconductivity.

Superconductivity in BiO1?xFxBiS2 and possible parent phase of Bi4O4S3 superconductor

We report the discovery of superconductivity in BiOFxBiS2, an isostructural compound of the REOFxBiS2 (RE: La, Nd, Pr, Ce, and Yb) superconductors. The parent compound, Bi2OS2, is nonsuperconductive. Superconductivity is observed in a wide range of F-doping content (0.06 x 0.27). The optimal F-doping concentration is about 0.24 in BiOFxBiS2, where the highest transition temperature of 3.5 K is achieved. We suppose that the superconductivity in BiOFxBiS2, as well as that in Bi3O2S3 and Bi4O4S3, is induced by partial substitution or insertion in the Bi2OS2 parent phase.

Drive the Dirac electrons into Cooper pairs in SrxBi2Se3

Topological superconductors are a very interesting and frontier topic in condensed matter physics. Despite the tremendous efforts in exploring topological superconductivity, its presence is however still under heavy debate. The Dirac electrons have been proven to exist on the surface of a topological insulator. It remains unclear whether and how the Dirac electrons fall into Cooper pairing in an intrinsic superconductor with the topological surface states. Here we show the systematic study of scanning tunnelling microscope/spectroscopy on the possible topological superconductor SrxBi2Se3. We first demonstrate that only the intercalated Sr atoms can induce superconductivity. Then we show the full superconducting gaps without any in-gap density of states as expected theoretically for a bulk topological superconductor. Finally, we find that the surface Dirac electrons will simultaneously condense into the superconducting state within the superconducting gap. This vividly demonstrates how the surface Dirac electrons are driven into Cooper pairs.

Superconductivity in Vacuum Annealed Bi6O8S5

Bi6O8S5, the parent compound of the Bi4O4S3 superconductor, is found to display typical insulating behavior via transport measurement. Here we report that the samples annealed at 200 and 250 °C in vacuum exhibit superconductivity below around 4.2 K. Samples annealed at neighboring temperatures also display superconducting transitions in the ρ∼ T curves, but no diamagnetic signals are observed in the \(M\sim T\) curves. Comparison of the XRD patterns for the samples before and after annealing suggests visible shrinkage of the lattice parameters in the superconducting samples. The phenomenon coincides with the case of the annealing induced superconductivity for FeTe0.8S0.2.

Superconducting properties of BiSe2-based LaO1−xFxBiSe2 single crystals

F-doped LaOBiSe2 superconducting single crystals with typical size of are successfully grown by flux method and the superconducting properties are studied. Both the superconducting transition temperature and the shielding volume fraction are effectively improved with fluorine doping. The LaO0.48F0.52BiSe1.93 sample exhibits zero-resistivity at 3.7 K, which is higher than that of the LaO0.5F0.5BiSe2 polycrystalline sample (2.4 K). Bulk superconductivity is confirmed by a clear specific-heat jump at the associated temperature. The samples exhibit strong anisotropy and the anisotropy parameter is about 30, as estimated by the upper critical field and effective mass model.

Pressure induced re-emergence of superconductivity in superconducting topological insulator Sr0.065Bi2Se3

The recent-discovered Sr

Pressure-induced reemergence of superconductivity in topological insulator Sr 0.065 Bi 2 Se 3

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Pressure-induced reemergence of superconductivity in topological insulator Sr[subscript 0.065]Bi[subscript 2]Se[subscript 3]

Bi

Experimental Investigation of Electronic Structure of La(O,F)BiSe2*

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Bulk superconductivity in single‐phase Bi3O2S3

Se