Extremely high upper critical field in BiCh2-based (Ch: S and Se) layered superconductor LaO0.5F0.5BiS2\u2212xSex (x\u2009=\u20090.22 and 0.69)

Masashi Tokunaga,Yosuke Goto,Kazuhisa Hoshi,Yoshikazu Mizuguchi,Ryosuke Kurihara

doi:10.1038/s41598-021-04393-3

Masashi Tokunaga, Yosuke Goto + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-04393-3

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Abstract

Centrosymmetric compounds with local inversion symmetry breaking have tremendously interesting and intriguing physical properties. In this study, we focus on a BiCh2-based (Ch: S, Se) layered superconductor, as a system with local inversion asymmetry, because spin polarisation based on the Rashba–Dresselhaus-type spin–orbit coupling has been observed in centrosymmetric BiCh2-based LaOBiS2 systems, while the BiCh2 layer lacks local inversion symmetry. Herein, we report the existence of extremely high in-plane upper critical fields in the BiCh2-based system LaO0.5F0.5BiS2−xSex (x = 0.22 and 0.69). The superconducting states are not completely suppressed by the applied magnetic fields with strengths up to 55 T. Thus, we consider that the in-plane upper critical field is enhanced by the local inversion symmetry breaking and its layered structure. Our study will open a new pathway for the discovery of superconductors that exhibit a high upper critical field by focusing on the local inversion symmetry breaking.

Highlights

Superconducting states are destroyed when a magnetic field is applied to the superconductor, and the maximum field is the upper critical field Bc2 in type-II superconductors
Theoretical studies have predicted that even if global inversion symmetry is preserved in a material, the breaking of local inversion symmetry leads to interesting physical phenomena such as parity-mixed superconductivity[9], stabilised odd-parity superconductivity[10], and the possibility of topological crystalline superconductivity with global centrosymmetric s ystems[11]
An anomalous Bc2 was observed in artificial superlattices composed of heavy-fermion superconductor CeCoIn5 and normal metal Y bCoIn5, wherein the inversion symmetry is locally broken at the interface between the CeCoIn5 layer, despite the fact that the global inversion symmetry is p resent[13]

Summary

Introduction

Superconducting states are destroyed when a magnetic field is applied to the superconductor, and the maximum field is the upper critical field Bc2 in type-II superconductors. Rashba-type spin–orbit coupling induced by locally non-centrosymmetric systems is expected to suppress the paramagnetic pair-breaking effect and enhance the Bc212. The crystal structure of the BiCh2-based superconductor possesses global inversion symmetry, whereas the inversion symmetry is locally broken in the B iCh2 layer.

Results

Conclusion