Study Of Physical Properties On Topological Semimetals Sr?Mn,Zn?Sb₂ And ZrSiSe

The subjects in our study to this thesis are the two kind layered topological semimetal.We start to alloy the Zn to Mn site of a potential magnetic topological semimetal SrMnSb₂ to another potential Dirac materials SrZnSb2.Taking X-ray diffraction and X-ray Energy dispersion to get the crystal orientation and concern the element content in our single crystals.When we present the superconducting quantum interferences devices?SQUID?to our samples.With the increase of Zn concentration,the beginning of a ferromagnetic and the antiferromagnetic coexistence has gradually changed to the spin glass then change into paramagnetic state;the transport measurement in the SrZnSb2 crystal found that quantum oscillations does not occurred in this crystal.Through the analysis of quantum oscillation,we explore and study the band structure with doping,which determine that the mixture bands does exist in SrMnSb₂.According to the data of maximum entropy processing,it is found the generation of a new band.The generation of this new band means an electron transition,i.e.Lifshitz transition.Secondly,we take another layered node-line semimetal ZrSiSe,the FS of ZrSiSe have been analyzed by AMR.Combination with the results by theoretical calculations,the evolution of the FS of ZrSiX?X=S,Se,Te?were concluded.This paper is divided into the following chapters:In chapter one,we mainly introduced the development process of topological electronic states,detailed discussed about the difference in topological semimetal,such as Dirac semimetal,Weyl semimetal and node-line semimetal.And then we simply introduces the analysis method of quantum oscillation such as the fast Fourier analysis the method and the maximum entropy method.In chapter two,replaced with Zn to Mn site of SrMnSb₂ on the crystal may be the magnetic Weyl semimetal,finally the SrZnSb2 single crystal materials also thought to be Dirac materials.Firstly we carried on their X ray diffraction?XRD?measurements to determine the crystal orientation and the size of the cell parameters.We use the X-ray energy dispersive analysis to determine its elemental composition.Finally we measured the magnetic properties and analyze the change of the band structure by analyze quantum oscillations,ARPES and theoretical calculations.The series of results give platform to study the evolution of band structure.In chapter three,the FS of ZrSiSe by angular dependence of magnetoresistance by us.Our results reveal the coexistence of quasi-two-dimensional?2D?and three-dimensional?3D?FS in this compound.With the enhanced SOC,low frequency bands exhibit a quasi-2D behavior in ZrSiSe when comparing with ZrSiS.However,the emergence of 2D FS in ZrSiTe arises from the electronic phase transition induced by charge transfer.The chapter four are the conclusions and outlooks.