Theory of the evolution of superconductivity in Sr2RuO4 under anisotropic strain

• Published in: npj quantum materials 2017-03, Vol.2 (1), p.1-7, Article 12
• Main Authors: Liu, Yuan-Chun, Zhang, Fu-Chun, Rice, Thomas Maurice, Wang, Qiang-Hua
• Format: Article
• Language: English
• Subjects: 639/766/119/1003; 639/766/119/995; Condensed Matter Physics; Contours; Electronic structure; Evolution; Excitation; Experiments; Fermi surfaces; Group theory; Momentum; P waves; Physics; Physics and Astronomy; Quantum Physics; Reconstruction; Shape; Spin density waves; Strontium ruthenium oxide; Structural Materials; Superconductivity; Surfaces and Interfaces; Switches; Thin Films; Topology; Transition temperature
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-017-0014-y

Sr 2 RuO 4 is a leading candidate for chiral p -wave superconductivity. The detailed mechanism of superconductivity in this material is still the subject of intense investigations. Since superconductivity is sensitive to the topology of the Fermi surface (the contour of zero-energy quasi-particle excitations in the momentum space in the normal state), changing this topology can provide a strong test of theory. Recent experiments tuned the Fermi surface topology efficiently by applying planar anisotropic strain. Using functional renormalization group theory, we study the superconductivity and competing orders in Sr 2 RuO 4 under strain. We find a rapid initial increase in the superconducting transition temperature T c , which can be associated with the evolution of the Fermi surface toward a Lifshitz reconstruction under increasing strain. Before the Lifshitz reconstruction is reached, however, the system switches from the superconducting state to a spin density wave state. The theory agrees well with recent strain experiments showing an enhancement of T c followed by an intriguing sudden drop. Condensed matter physics: strain drives evolution of superconductivity Intriguing superconducting properties appear upon anisotropic strain applied, with an insight revealed by the change of electronic structure. Yuan-Chun Liu and colleagues at the Nanjing University and collaborators in China and Switzerland studied the superconductivity and competing orders in Sr 2 RuO 4 under strain using functional renormalization group theory. An enhancement of superconducting transition temperature T c followed by a sudden drop can be traced from the evolution of Fermi surface, the contour of zero-energy excitations in momentum space in the single-particle band structure, and the development of a competing spin-density-wave order. In consistent with recent experiments, the results provide an understanding of the strain-driven superconductivity evolution by means of Fermi surface change. This work not only helps to reveal the microscopic origin behind the effect of strain on superconductivity, but also offers a solution toward manipulating superconductivity.