Uniaxial-strain tuning method in the study of iron-based superconductors

Abstract

In the study of quantum materials, pressure and strain that can change lattice parameters and symmetry are effective experimental methods for manipulating the electronic properties of the systems. In the measurements under hydrostatic pressure or in-plane epitaxial strain, the change in lattice parameter could lead to significant alterations in the electronic structure, thereby inducing novel quantum phenomena and phase transitions. In comparison, the in-plane uniaxial strain, which has been widely employed in recent years, not only changes lattice parameters but also directly breaks and controls the symmetry of the system, thereby affecting the electronic ordered states and even collective excitations of the systems. This review article aims to provide a comprehensive overview of the basic concepts of uniaxial strain, the development of experimental methods, and some research progress in using these methods to tune superconductivity and electronic nematicity in iron-based superconductors. This review contains six sections. Section is a genetral introduction for the uniaxial strain techque and discuss the arrangement of this paper. Section (2) introduces basic concepts and formulas related to elastic moduli and the decomposition of uniaxial strain into irreducible symmetric channels under <i>D</i>_4<i>h</i> point group. Section (3) gives an introduction to iron-based superconductors (FeSCs) and discuss the uniaxial-pressure detwinning method and related research progress. Section (4) introduce the establishment of the elastoresistance as a probe of the nematic susceptibility and discuss the key research works in this direction. Section (5) describes the research progress on the effects of uniaxial strain on superconductivity and nematicity. In sections (4) and (5), key experimental techniques, such as elastoresistance are discussed in detail. Section (6) expands the discussion to several class of quantum materials suitable for uniaxial-strain tuning method beyond the FeSCs. Finally, we give an brief summary and perspective to the uniaxial strain tuning technique. Overall, this review article aims to serve as a valuable resource for the beginners in the field of FeSC and those who are interested in using uniaxial strain to tune the electronic properties of quantum materials. By summarizing recent advancements and experimental techniques, this review hopes to inspire further research and innovation in studying correlated electron materials under uniaxial strain.