Superconducting Properties of BiS2-Based Layered Compounds

BiS2-based layered compounds constitute a distinctive family of low-temperature superconductors, in which alternate stacks of BiS2 conduction layers and various blocking layers give rise to a rich interplay between structure and electronic properties. Since the initial discoveries in Bi4O4S3 and LaO1−xFxBiS2, the superconducting transition temperature (Tc) has been tuned by carrier doping, external pressure, chemical substitution and control of in-plane chemical pressure. The relatively large spin–orbit coupling of bismuth 6p orbitals, coupled with local inversion symmetry breaking in the BiS2 layer, leads to unconventional features such as enhanced upper critical fields and directional anisotropy of the superconducting gap. Studies have revealed the importance of multiband conduction, suppression of in-plane disorder and structural phase transitions from tetragonal to monoclinic symmetry as key factors in tailoring superconducting behaviour. These compounds offer a versatile platform for exploring novel pairing mechanisms and high-field applications in quantum devices.

Research from Nature Portfolio

Recent studies have demonstrated that local inversion symmetry breaking within the BiS2 layers can dramatically enhance the in-plane upper critical field (Hc2). Investigations of LaO0.5F0.5BiS2−xSex revealed that substitution of selenium induces a layered environment lacking an inversion centre, enabling spin-orbit coupling to sustain superconductivity under magnetic fields up to 55 T. This finding points to new strategies for designing high-field superconductors. Complementary work on high-pressure phases of (Sr,La)FBiS2 has shown that a monoclinic structural distortion drives a conventional isotope effect on Tc, in contrast to tetragonal BiS2 systems displaying unconventional shifts. This implies that the pairing mechanism can switch between phonon-mediated and more exotic routes as symmetry changes under pressure.

Superconducting Properties of BiS2-Based Layered Compounds publication trend

The graph below shows the total number of articles in superconducting properties of bis2-based layered compounds across all publications each year (not limited to Nature Index journals).

Technical terms

Superconducting transition temperature (Tc): The critical temperature below which a material exhibits zero electrical resistance and perfect diamagnetism.

Upper critical field (Hc2): The maximum magnetic field strength at which a superconductor remains in the superconducting state.

Carrier doping: Introduction of additional electrons or holes into a material to alter its electronic properties and induce superconductivity.

Chemical pressure: Lattice strain within the conducting layers induced by atomic substitution, effectively simulating external pressure.

Multiband conduction: Electrical transport involving more than one energy band crossing the Fermi level, affecting superconducting properties.

Nematic superconductivity: A superconducting state that breaks rotational symmetry, leading to directional dependence of electronic properties.

References

1. Discovery of a Superconductor Bi5O4S3Cl Containing the Unique BiS3 Layer. Advanced Science (2023).
2. Material Development and Physical Properties of BiS2-Based Layered Compounds. Journal of the Physical Society of Japan (2019).
3. In-plane chemical pressure essential for superconductivity in BiCh2-based (Ch: S, Se) layered structure. Scientific Reports (2015).
4. Two-fold symmetry of in-plane magnetoresistance anisotropy in the superconducting states of BiCh2-based LaO0.9F0.1BiSSe single crystal. Journal of Physics Communications (2020).
5. Extremely high upper critical field in BiCh2-based (Ch: S and Se) layered superconductor LaO0.5F0.5BiS2−xSex (x = 0.22 and 0.69). Scientific Reports (2022).
6. Possible pairing mechanism switching driven by structural symmetry breaking in BiS2-based layered superconductors. Scientific Reports (2021).
7. Experimental overview on pairing mechanisms of BiCh2-based (Ch: S, Se) layered superconductors. Journal of Physics Condensed Matter (2021).