Development Of Laser-based Angle Resolved Photoemission System And Study Of ZrTe_3-xSe_x Material

Superconductivity has always been one of the vibrant topics in physics due to its rich nature since its discovery.The conventional superconducting materials and theories have been continuously developed,meanwhile,the discovery of unconven-tional superconductors and high-temperature superconductors has led to an upsurge of study in the field of superconductivity.As an experimental method to directly de-tect the electronic structure of materials,ARPES plays an irreplaceable role in the research process.To develop Large Momentum Ultra-Low Temperature Ultraviolet Laser-Based Angle Resolved Photoemission System with ultra-high resolution can s-tudy quantum phase transition and high temperature superconductivity mechanisms under extremely low temperature conditions.Some Transition Metal Chalcogenides have the property of charge density wave(CDW).It is also great significant to study the origin and evolution of CDW.In this thesis,describing the design and development of Large Momentum Ultra-Low Temperature Ultraviolet Laser-Based Angle Resolved Photoemission System,the ARPES study of charge density wave material ZrTe3 and the ZrTe3-xSqx doped with different concentrations of Se,the single-crystal growth of CeCoIn5 and the design and development of Molecular Beam Epitaxy(MBE)system.The thesis contains the following main contents:1.The basic properties and development process of superconducting materials are introduced,as well as the theoretical development of conventional supercon-ducting materials,and the development of the theory and materials of CD-W which are directly related to this thesis,and the research background of ZrTe3-xSex system and heavy Fermion material CeCoIn5.2.The principle and experimental technique of ARPES are introduced.The appli-cations of light source,electron energy analyzer,vacuum system and cryogenic technology in ARPES are introduced in detail,and the ARPES systems related to the thesis in our laboratory are introduced.The advantages of Laser source with ultra-high energy resolution and momentum resolution are introduced.3.Describing in detail the design and development of Large Momentum Ultra-Low Temperature Ultraviolet Laser-Based Angle Resolved Photoemission Sys-tem,through cooperatively designing 3He cryogenic bench,through multilayer thermal radiation shielding and precooling by liquid nitrogen and liquid heli-um(4He),achieving the circulation of 3He,the sample temperature could be up to below 1K and achieve the ultra-low temperature condition.through the co-designed ultraviolet laser source of approximately 7.5eV,greater momentum space detection can be achieved on the basis of the assurance of ultra-high res-olution.In addition,the system is equipped with 7eV laser and a gas discharge light source.Through several experimental attempts,the optimal annealing con-ditions for the demagnetization of the stainless steel wire used in the ultra-high vacuum chamber were found,and the residual magnetism of the components in the chamber was successfully removed.The development process of the system is introduced specifically,from the location,design drawings and instrument support to the assembly and construction,participating in the whole process of the instrument development.The preliminary test results of the instrument are introduced.The performance of the motor used in the experiment can meet the good linear relationship,and the rotation angle ? is positioned and tested,and the basic requirements for the rotation along the sample axis can be achieved.A preliminary test of the system was performed using a Helium lamp and a 7eV laser light source,and a clear Bi2Se3 energy band structure was obtained under Helium lamp conditions.4.ZrTe3 material is systematically study by utilizing three different photon energy sources in our laboratory.First,using the Helium lamp with photon energy of 21.2eV to observe the appearance of the CDW state in the D-point area where CDW occurs directly.Focusing on the electronic structure of the central three-dimensional Fermi surface around ? point area,the 7eV laser system combined with the time-of-flight new energy analyzer to clearly observe the splitting char-acteristics around the ? point band,and for the first time,found the anomalous scattering rates and weak electron-phonon coupling near the CDW temperature around the ? point,demonstrating that the central three-dimensional Fermi sur-face is also modulated by the CDW.5.The ARPES study was performed on two different doping concentrations of ZrTe3-xSex(x=0.01 and 0.04).For the 0.01 component sample with a CDW temperature of 45K,the anomalous scattering rates is observed in the three-dimensional Fermi surface region,whereas for the 0.04 component sample in which the CDW was suppressed,it is satisfied with the Fermi liquid theory.Quasi-one-dimensional Fermi Surface B-point area of two different composi-tions are study by using Helium lamp of 21.2eV and a circularly polarized 7 eV laser and 11eV Laser,high-resolution results suggest clear electronic structure and two sets of bands around B region.Focusing on the electronic structure of the quasi-one-dimensional Fermi surface of the 0.01 component sample by us-ing 11eV laser,a detailed study was made of the evolution of the energy band structure along the BD direction,and observed the evidence of CDW energy gap opening in the D-point area.A detailed variable temperature experiment was performed on the D point,and the gap was observed above CDW temperature,this result indicated that existing the behavior of pseudogap on this system.6.The growth of single crystal of heavy Fermion material CeCoIn5 is introduced.The MBE equipment with growing heavy Fermion thin film and the transfer chamber interconnected with MBE and ARPES are designed.