Ferroelectric soft phonons, charge density wave instability, and strong electron-phonon coupling in BiS2 layered superconductors: A first-principles study
T. Yildirim
DOI 10.1103/PhysRevB.87.020506 · Physical Review B
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Abstract
Very recently a new family of layered materials, containing BiS2 planes, was discovered to be superconducting at temperatures up to Tc=10 K, raising questions about the mechanism of superconductivity in these systems. Here, we present state-of-the-art first-principles calculations that directly address this question and reveal several surprising findings. The parent compound LaOBiS2 possesses anharmonic ferroelectric soft phonons at the zone center with a rather large polarization of ≈10 μC/cm2. Upon electron doping, new unstable phonon branches appear along Q=(q,q,0), causing Bi/S atoms to order in a one-dimensional charge density wave (CDW). We find that BiS2 is a strong electron-phonon coupled superconductor in the vicinity of competing ferroelectric and CDW phases. Our results suggest directions to increase Tc in this new class of materials.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| LaO0.5F0.5BiS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8.5 | Pressure not reported | unknown |
| LaO0.5F0.5BiS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 6 | Pressure not reported | unknown |
| Bi4O4S3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 10 | Pressure not reported | unknown |
| LaOxF1-xBiS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 10 | Pressure not reported | unknown |
| NdOxF1-xBiS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 10 | Pressure not reported | unknown |
| PrOxF1-xBiS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 10 | Pressure not reported | unknown |
| CeOxF1-xBiS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 10 | Pressure not reported | unknown |
| Ba1-xKxBiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 31 | Pressure not reported | unknown |
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