Universal V-shaped temperature-pressure phase diagram in the iron-based superconductors KFe2As2, RbFe2As2, and CsFe2As2

作者：Tafti F F^*; Ouellet A; Juneau Fecteau A; Faucher S; Lapointe Major M; Doiron Leyraud N; Wang A F; Luo X G; Chen X H; Taillefer Louis

来源：Physical Review B, 2015, 91(5): 054511.

DOI：10.1103/PhysRevB.91.054511

We report a sudden reversal in the pressure dependence of T-c in the iron-based superconductor RbFe2As2, at a critical pressure P-c = 11 kbar. Combined with our prior results on KFe2As2 and CsFe2As2, we find a universal V-shaped phase diagram for Tc versus P in these fully hole-doped 122 materials, when measured relative to the critical point (P-c, T-c). From measurements of the upper critical field H-c2(T) under pressure in KFe2As2 and RbFe2As2, we observe the same twofold jump in (1/T-c) (-partial derivative H-c2/partial derivative T) T-c across P-c, compelling evidence for a sudden change in the structure of the superconducting gap. We argue that this change is due to a transition from one pairing state to another, with different symmetries on either side of P-c. We discuss a possible link between scattering and pairing, and a scenario where a d-wave state favored by high-Q scattering at low pressure changes to a state with s(perpendicular to) symmetry favored by low-Q scattering at high pressure.

• 出版日期2015-2-17
• 单位中国科学技术大学