s±-pairing symmetry defining High order topological superconductor
The field of topological phases of matter and high-Tc superconductivity, as important and vibrant as they are individually, have almost had no overlap until very recently. Due to the discovery of intrinsic topological properties in iron based superconductors, the two fields have begun to interact. Iron based superconductors have become a high-temperature platform for realizing topological superconductivity and Majorana modes, attracting enormous interests from fundamental science such as topological quantum computation. However, the unique property, the unconventional pairing in these high-Tc superconductors has not been involved. Recently, Prof. Jiangping Hu at IOP, together with his collaborators, propose a new class of topological superconductors (TSC) which are induced by the unconventional pairing.
This new class of TSC represents a boundary-obstructed higher order topological state of matter which can only be formed by sign-changed unconventional pairing, the promising s±-wave pairing in iron pnictides. They predict the 112-family of iron pnictides, which contains an intrinsic topological insulator/high Tc superconductor heterostructure, to be the material candidate for our proposal. Because of the boundary-obstruction, the topologically non-trivial feature of the 112 pnictides does not reveal itself in a bulk-only torus band analysis without boundaries. The main is sketched in Fig.1.
This work significantly advances the understanding of TSC and offers a promising high-temperature platform for Majorana modes. Most importantly, it provides a novel way to unambiguously identify the extended s-wave order in the iron pnictides, setting up a strong connection between topological phases of matter and unconventional superconductivity fields.
The work titled as "Boundary-Obstructed Topological High-Tc Superconductivity in Iron Pnictides" was published on Physical Review X, 10,041014 (2020)。Link: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.041014
The study was supported by the National Science Foundation, the Ministry of Science and Technology of China, the Chinese Academy of Sciences.
Fig.1 The sketch of Fermi surfaces, s±-wave pairing and corner/hinge Majorana states.