铁基超导研究中的单轴应变调控方法

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

在超导和强关联电子材料的研究中,通过引入压力和应变改变晶格参数和对称性,是调控体系电子性质的有效实验手段.在静水压和外延薄膜面内应变的调控中,晶格参数的变化可以引起电子结构的显著改变,进而诱导出新奇的物理现象.相比这两种方法,近年来开始被广泛采用的单轴应变调控方法,除了可以改变晶格参数,还可以直接破缺和调控体系的对称性,影响体系的电子有序态乃至集体激发.弹性单轴应变作为对称性破缺场,可以作为电子向列相及其涨落的探针;应变对超导和电子向列相的调控,也可以为理解体系中电子态的微观机制提供实验依据.本文将介绍单轴应变调控的基本概念、实验方法的发展,以及采用这些方法调控铁基超导体中的超导和电子向列相等方面的一些研究进展,并简单介绍单轴应变在其他量子材料中的应用.

In the study of quantum materials,introducing pressure and strain that can change lattice parameters and symmetry is an effective experimental method for manipulating the electronic properties of the system.In measurements under hydrostatic pressure or in-plane epitaxial strain,the changes in lattice parameters will lead to significant changes in the electronic structure,thereby triggering off novel quantum phenomena and phase transitions.By comparison,the in-plane uniaxial strain,which has been widely employed in recent years,not only changes lattice parameters,but also directly destroys and controls the symmetry of the system,thereby affecting the electronic ordering state and even collective excitation of the system.This article provides a comprehensive overview of the basic concepts of uniaxial strain,the development of experimental methods,and some research progress in using these methods to regulate superconductivity and electronic nematicity in ironbased superconductors.This review contains six sections.Section 1 focuses on a genetral introduction for the uniaxial strain techque and the arrangement of this paper.Section 2 is devoted to the basic concepts and formulas related to elastic moduli and the decomposition of uniaxial strain into irreducible symmetric channels under D_(4h) point group.Section 3 gives iron-based superconductors(FeSCs) and discusses the uniaxial-pressure detwinning method and related research progress.Section 4 introduces the establishment of the elas tores is tance as a probe of the nematic susceptibility and discusses the key researches in this direction.Section 5 describes the research progress of 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 extends the discussion to several types of quantum materials suitable for uniaxial-strain tuning method beyond the FeSCs.Finally,we provide a brief summary and outlook on the uniaxial strain tuning technique.Overall,this review article provides valuable resources for the beginners in the field of FeSC and those who are interested in using uniaxial strain to modulate the electronic properties of quantum materials.By summarizing recent advancements and experimental techniques,this review hopes to inspire further research and innovation in studying electronic materials under uniaxial strain.