Field-induced superconductivity in transition metal dichalcogenides

Jianting Ye

Device Physics of Complex Materials, Zernike Institute for Advanced Materials, Groningen, The Netherlands

Superconductivity can be induced in the electric-double-layer (EDL) transistors made by layered transition metal dichalcogenides (TMD) [1]. The electric field in the EDL gating breaks the inversion symmetry at the interface between ion and TMDs, which dramatically modifies the bulk energy band by establishing a direct gap between conduction and valence bands at the edges of Brionllion zone. The spin degeneracy is lifted at the K/K’ point by the out-of-plane Zeeman type spin orbit coupling (SOC). In the ion-gated TMD flakes, this effective Zeeman type SOC exhibits strong protection to superconductivity by making Ising-like pairing between the K and K’ point, which manifests as significantly enhanced in-plane upper critical field in the magneto-transport. We found an order of magnitude increase of the upper critical field than the bulk superconducting phases, where the same Zeeman type SOC is eliminated by interlayer coupling [2]. The ionic gating not only induces dense charge carriers but also changes the electronic structure by breaking inversion symmetry, which together with spin-orbit coupling can develop novel property in the interface superconductivity.

References

[1] J. T. Ye, Y. J. Zhang, et al., Science 338, 1193 (2012).

[2] J. M. Lu, O. Zheliuk, et al., Science 350, 1353 (2015).