Scanning Tunneling Microscope/Spectroscopy Investigation Of Iron-Based Superconductors Under Uniaxial Stress

In recent years,the discovery of topological band structure in iron-based super-conductors has connected two of the most active research fields in condensed matter physics:unconventional high-temperature superconductors and topological quantum states.Topological iron-based superconductors have become one of the most promis-ing Majorana platforms due to their characteristics of high superconducting transition temperature,single material and large topological energy gap.Now,Majorana zero modes（MZMs）have been almost precisely verified by the discovery of pure zero bias peaks in the magnetic vortex cores or topological defects of a number of iron-based superconductors.The investigation of quantum engineering has gradually replaced the investigation of physical properties in the study of topological iron-based superconduc-tors.One of the most important steps in this process will be learning how to accurately manipulate the Majorana zero modes.In order to achieve the manipulation of iron-based Majorana platforms,we devel-oped an in-situ uniaxial stress device adapted to angle-resolved photoemission spec-troscopy（ARPES）and scanning tunneling microscopy（STM）.Uniaxial stress is an important technique used to study unconventional superconductors.Uniaxial stress,in contrast to hydrostatic pressure,has the ability to alter the symmetry of the system.When the stress is applied along a given lattice direction,the sample’s topological char-acteristics and superconductivity are also altered.This paper will systematically introduce the manipulation of LiFeAs single crystal samples using in-situ uniaxial stress.With uniaxial stress in the direction[110],the chemical potential of LiFeAs moves downward relative to the overall band structure and is closer to the topological insulator surface state.Using uniaxial stresses in the direction[100],the chemical potential of LiFeAs moves upward relative to the overall band structure,closer to the topological Dirac semimetals state.Uniaxial stress can be used to achieve the topological vortex phase transition and control the presence and disappearance of the Majorana zero modes.Then this paper will introduce the surface superconductivity observed in undoped Ba Fe₂As₂,which is induced by uniaxial stress and room temperature relaxation.Finally,this paper will summarize and prospect how to use the iron-based Majorana platform to make quantum devices.Our research aimed to help readers deepen their understanding of the physical mechanism of Majorana and promote the development of topological quantum engineering.