The Crystal Growth And Physical Properties Of Iridium Oxide Compound SrIr₂O₆ And Others Materials

The study of new materials exploration and physical properties is an important research direction in condensed state physics.More than thirty years ago,the discovery of high-temperature superconductivity of copper oxides and the quantum Hall effect led to great developments in the field of strong correlation and topology.Nowadays,research on strong correlation systems and topological materials is proliferating,single crystal growth plays an important role in the part of materials synthesis.Materials in this field have also been prepared and studied in this work.In this dissertation,combined with single crystal growth,structural and physical properties and ARPES measurements,we observed the crystalline,electronic and magnetic properties and band structures of some materials.The main results of this dissertation are summarized as follows:1.The crystal growth and physical properties of SrIr₂O₆.It is found that poly crystalline SrIr₂O₆ sample shows Curie-Weiss behaviors at high temperatures.With temperature decreasing,the resistivity increase.The material exhibits no magnetic order down to 0.05 K and its low-temperature magnetic properties have non-trivial gapless paramagnetic behaviors,showing as the power law behaviors of the magnetic susceptibility and zero-field specific heat.It is important to prepare SrIr₂O₆single crystals successfully for the understanding of their intrinsic behaviors and anisotropic properties.The measurement of physical properties shows that single crystals SrIr₂O₆ samples has the similar behaviors with poly crystalline SrIr₂O₆samples.Our results provide strong evidences for the existence of the random singlet phase in SrIr₂O₆,which suggests that the strongly correlated electron systems can host such phase.2.The single crystal growth and physical properties of EuSn₂As₂.This work introduce the synthesis of EuSn₂As₂ single crystals by Sn-flux method.A previous study reveals that EuSn₂As₂ undergoes a transition from a paramagnetic?PM?phase to an antiferromagnetic?AFM?phase near 25 K.Because of the hole-doped samples,conventional Angle resolved photoemission spectroscopy?ARPES?measurements cannot obtain the information in the band gap.Instead,we use time-resolved ARPES?tr-ARPES?with the pump-probe method to measure the unoccupied electronic states.As a result,the topological surface states of the Dirac type in the band gap are successfully observed.This is the first time that the clear topological surface state has been observed in a magnetic topological insulator.3.Growth of monolayer and bilayer MoS₂ flakes.There are much difficulty to growth MoS₂ flakes,such as difficulty of mass produce,the small area of the film and the uncontrolled number of layers growth.In this work,we based on the traditional Chemical Vapor Deposition?CVD?methods,by using of solution precursor,grown MoS₂ flakes at 750^?.This method reduces the supersaturation level of the precursor vapor and the nucleation density,yielding clean monolayer and bilayer films.The thicknesses of MoS₂ flakes were measured to be about 1.28nm corresponding to bilayer MoS₂.The Raman shifts are about 18.8 cm^-1and 20.9 cm^-1,corresponding to the monolayer and bilayer MoS₂ flakes.Those are my main thesis works.Strong correlation systems and topological materials,as two topic issues in condensed matter physics,are still a lot of problems to be solved,and there is a need for researchers to study more materials.